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Recursion is a phenomenon in mathematics and computer science where an equation refers to itself, allowing a finite function to represent an infinite set of objects. In physical terms, it is similar in structure to Russian Matryoshka dolls, which are designed to nest one inside the other.

The basic types:

The "Russian Doll World" — the worlds are physically inside one another. The most common way to travel between them is changing size. This dates back to the sci-fi pulps of the 1930s, even though the atomic model that likely inspired this trope (where electrons orbited the nucleus like planets around a sun) had been superseded as early as 1925.
The Nested Story — One of the oldest examples is The Arabian Nights. Scheherazade tells stories of people who tell stories about people who tell stories, and so on. This is basically a Story Within a Story or Framing Device. (Layers deep, that is.)
The Recursive Simulacrum, or "Matrix Hypothesis" — Building a ship in a bottle, on a ship in a bottle, basically. Someone creates an artificial world, be it a computer simulation, virtual reality, pocket universe or a miniature planet. Then someone in that world creates another simulacrum. Bonus points if an inhabitant of the last simulacrum builds another one, or the original creator's world turns out to be a model itself. Game Within a Game and Reality-Changing Miniature are subtropes.
The Dream Within a Dream — A character dreams of another world, is put into a Lotus-Eater Machine or starts hallucinating another life, and to emphasize the drama of the situation, the character's confusion and/or the depths of their madness, the character is pushed into a layer within or thinks they have escaped into the real world, only to find they are simply in an outer layer of the dream.
Transfictionality — Suppose Recursive Canon (a copy of the work itself, or a related work by the same author) shows up within the work. Then it turns out to be real, because the author of the Story Within a Story (who may or may not be the author of the actual work) is, in fact, God of his own sub-created universe. May result in Fridge Horror (or regular horror if it's addressed by the plot) if the in-story author has a Creator Breakdown. See also Rage Against the Author.

For extra headache-inducing potential, a creator might mix and match:

Stable Fictional Loop - Similar to a Stable Time Loop but with narration instead of time travel, this can take any of the above forms and turn it into a paradox, such as a pair of Alternate Universes that reference each other through recursive fiction, usually with paradoxical event flags that prevent you from determining which version of the story is the "outer" story, or which is the "real" story. Compare Trapped in TV Land.
Turtles All The Way Down - It's an infinite regress; there is no "reality". No matter how far up or down you go, you can't get out. Perhaps they Ascended to a Higher Plane of Existence or they're in a Dying Dream. Perhaps they're simply insane. If lucky, it's a Multi User Shared Hallucination, not a Solipsistic Nightmare. (The name comes from a famous "argument" for the Turtle Island cosmology as an explanation for gravity.)
Single reality - There is only one world, that is somehow enclosed inside itself. Possibly in several instances.

A similar phenomenon in art and graphic design is the Droste effect, where a picture includes a smaller copy of itself, that copy has a smaller copy of itself, and so on.

Note that there has to be more than two layers shown or implied, or a path inward must paradoxically lead to the outer world (which is closer to an actual recursive equation.) Otherwise it likely falls under one of the simpler Otherworld Tropes. Shrinking into a subatomic world, for instance, does not count as a Recursive Reality unless a character can shrink further and find an even smaller world within, or somehow end up back where they started.

Recursive Canon is a specific subtrope where the work postulates its own existence in-story, or a fictional version of the author also exists in-story (allowing the characters to criticize it or the author or change it, of course.) Compare Mutually Fictional.

Not to be confused with Direct Line to the Author, where the work postulates its own existence in real life, or the existence of a fictional author in real life (as "researched" by the real author, of course.) Compare Daydream Believer, Mythopoeia.

Compare with most Otherworld Tropes, particularly Expendable Alternate Universe, where the importance of all these alternates is downplayed by the assertion of a "real world", Matrix Hypothesis (also known as Recursive Reality), and Up the Real Rabbit Hole, where the "prime" level of existence is called into question. The latter is often paired with Recursive Reality for its headache-inducing potential. See also Daydream Believer, Welcome to the Real World.

Also, try to keep in mind the MST3K Mantra while reading any of the examples. Believe us, it's just not worth it to lose your sanity to these. Because a recursive reality is physically impossible and never will happen.

Compare Meta (things that refer to or are about themselves).

Spoileriffic trope, as the layering is usually a major plot twist.

Examples:

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Anime & Manga

Mount Head: A man grows a cherry tree out of his head. The man eventually pulls the tree out of his head by the roots. Unfortunately for him this leaves a depression on the top of his head, which fills with water when it rains, forming a lake. A lake that crowds of people visit, just as they were visiting the cherry tree. The man then somehow visits the top of his own head, going to the lake. This is followed by a really trippy sequence in which the camera continually zooms in to the man on top of his head, visiting his lake...then zooming in to the top of his head, where of course there's a lake, which he is visiting...then zooming in to the top of his head again...
The entirety of Shimeji Simulation's Chapter 42. The first part shows Shijima and Majime in what appeared to be an empty, barren area with a mysterious donut-shaped structure and a noose within the middle, of which Mogawa attempted to hang herself. Then the scene cuts to another recursion where Shijima, Majime and Sumida are seen in an art gallery-esque place, with Sumida seen painting Mogawa that turned out to be the previous recursive world that Shijima and Majime just visited moments ago. And then the final scene cuts to the final recursion where a small, crude canvas sitting on an easel of what looked like the members of Hole-Digging Club including Shijima and Majime. Shijima and Majime are later seen at the final panel of the chapter.
One chapter in Yakitate!! Japan has Azuma pulling out a copy of the tankobon the chapter is in to show that a Reality Warper reaction to eating nori spread was strong enough to temporarily change the title of the manga on the cover (which it even does in real life.)

Arts

Comic Books

All-Star Superman shows Superman, wondering how the world will function without him, creating a miniature Earth in a miniature universe. It grows relatively quickly, and the last panel of the issue shows someone drawing a comic-book character, declaring "This time, I'll change everything..." The character is Superman - it's our world, the man doing the drawing is Joe Shuster, and we have a loop.
The Marvel Vs. DC crossover and the Amalgam Universe that resulted was explained by setting Marvel and DC continuities (each with their own fiction, past, present and future, parallel dimensions and alternate timelines) in discrete multiverses created by entities called "The Brothers". Those guys live in the "Omniverse", which supposedly contains every real and fictional universe ever. The Brothers are often interpreted by fans as being forms of Marvel's "The One Above All" and DC's "The Presence", each of which is God in their respective universe.
Astro City has the Moleculands, an entire set of microscoping realities like Subatomia and the Quarkrealms.
A short Darkwing Duck comic published in an issue of Disney Adventures (titled "Cogito Ergo Something") has Launchpad holding up a dandelion and positing the existence of countless Recursive Realities to Darkwing. Sure enough, the perspective changes, and we see another world inside the dandelion seed where an alien Launchpad is presumably saying the same thing to an alien Darkwing about an alien flower. Then the perspective changes to inside the alien flower, and we see the "normal" world again (inside the inside), where Darkwing promptly blows the whole idea off as nonsense and blows the dandelion seeds to the wind.
Fables mentions this trope with a side-character. A queen is punished for her infidelity to her sorcerer-king husband by being transformed into a tortoise, cursed to wander with a fragile teacup balanced on her shell, with the teacup containing the archipelago on which she grew up. Later we see a short story where there is a tradition amongst the people of the archipelago to touch the "wall" surrounding their sea, and it turns out there is a debate in their community between people who hold different views on whether the tortoise exists or not, and whether there are Turtles All The Way Down. As far as the reader can tell, both schools of thought are wrong, unless it subsequently turns out that the greater Fables multiverse is on a tortoise of its own.
- The Great Fables Crossover introduces the Fables (who have long theorised that the popularity of their stories amongst the mundane humans of Earth are tied to their own power, though this has never been conclusively proven, and nobody's sure whether they exist because of the Mundies' stories, or if the Mundies have stories about them because they already existed) to the Literals (who are the embodiments of literary devices, like the Anthropomorphic Personifications of Revision, Genres, the Deus ex Machina, and their progenitor, the Pathetic Fallacy, Anthropomorphic Personification of Anthropomorphic Personifications). The antagonist of this arc is Kevin Thorn, (son of the Pathetic Fallacy, father of Revise) who, as the personification of story-telling itself, has gotten thoroughly fed up with his characters all acting on their own and making a mess of his overall story, and has resolved to rewrite things so that the entire Fables multiverse (including their equivalent of the Mundy world) never existed in the first place, but fortunately his braindead twin Writer's Block keeps preventing him from actually making the multiverse-ending flourish of his pen. The screwing around with Meta-Concepts, breaking of the Fourth Wall (which the Literals are aware of but the Fables aren't) and general Bizarro Episode feeling of this arc causes Bigby and Snow to make the decision to treat it as an in-universe Big-Lipped Alligator Moment, and try to get back to their already-complicated lives as quickly as possible.
Grant Morrison's The Filth shows several microcosm-style environments (including a city contained by an enormous ship and a miniature world populated by "I-Life"). The Hand's base, The Crack, is implied to be a microscopic base created to harvest the ink leaking out of the pen Greg uses to write the note for his (probably failed) suicide. The Crack, in turn, is home to the Paperverse, the fictional reality that The Hand mines for exotic technology.
Hasse's He Who Shrank inspired a number of similar comic book stories: Lost In The Microcosm (Weird Science #1, 1950), The World Beyond (Strange Tales #122, 1954) and I Shrunk Away to Nothing! (Journey Into Mystery #56, 1960), the latter two published by Atlas, the predecessor to Marvel Comics.
The ending to Irredeemable is basically this: Plutonian having to absorb deadly radiation surrounding Earth or be killed with a weapon so powerful it can kill him completely. After he does so his body begins to be slowly ravaged. As chance to finally redeem Plutonian, Qubit uses inter-dimensional technology to send Plutonian's original essence before his Face–Heel Turn to a parallel universe where he can end up right. As a result Plutonian's essence inspires Joel Shuster and Jerry Siegel to create Superman which in turn gets Mark Waid into comics and eventually writing Irredeemable.
Marvel's Microverse was originally treated as one of many microscopic universes, but it was retconned to Another Dimension accessed by shrinking so far that one crosses the Pym Barrier. Also, once in the Microverse, characters cannot shrink any further.
- In one tale, the cosmic entity Kubik was educating the younger cosmic entity Kosmos on the structure of the universe by growing from the mortal level through the galactic, eventually becoming larger than the universe, then larger than the trans-cosmic realm where universes exist ... only to pop up to the level of quarks, and growing up past the atomic level back to the mortal realm. As Kubik said it; "The center of the universe is wherever you happen to be at the moment."
Warren Ellis's Planetary sums it up best itself:
- "This is the shape of reality. A theoretical snowflake existing in 193,833 dimensional space. The snowflake rotates. Each element of the snowflake rotates. Each rotation describes an entirely new universe. The total number of rotations are equal to the number of atoms making up the Earth. Each rotation makes a new Earth. This is the multiverse."
- Said by someone who developed a quantum computer in 1945 which uses the shape of the multiverse to compute and create situations upon their Earth to solve problems. That's right: using the entire multiverse to effect changes upon one single world within it. So fractal it hurts.
The crossover miniseries Star Trek: The Next Generation/Doctor Who: Assimilation² (obviously) has the Doctor meeting the TNG cast, whereas previously, episodes of the regular Doctor Who show referenced Star Trek as a fictional series. He lampshades it in his own typically enigmatic fashion, casually remarking that he can feel his memories changing after he enters the Trekverse— he recognizes Worf as a Klingon, but recalls that he didn't know the word a few minutes ago.
Wonder Woman: Atomia's "Atom World" can be accessed by being shrunk down to a minuscule microscopic size.

Comic Strips

In a reversal of the He Who Shrank scenario, Calvin once grew to the size of a galaxy and finds a door that leads back to his own room.
Dilbert sort of has a "Turtles All The Way Down" example.
Guy: Some say the earth is on the back of a giant turtle. But who do you think is holding the turtle?
Dilbert: You?
Guy: Wrong! It's turtles all the way down. But who do you think is holding the infinite turtles?
In an early FoxTrot Sunday Strip, the very strip's splash panel can be seen on a newspaper that Roger is reading.
A Pearls Before Swine comic strip featured Pig meeting Atlas who held the Earth on his shoulders. Pig then points to the part of the Earth where he is, and his giant hand comes down and pokes his eye.

Fan Works

Arai-san Mansion: The floor Ж-13-А-7 features a toy shop. Raccoon plays with a miniature toy shop and is amused by the miniature Raccoon and Fennec inside, while a giant hand moves the furniture around. Fennec quickly tells her to stop touching it. When another Friend pulls out a doll that looks like herself, a hand grabs her off screen. The elevator attendant puts the doll back and the Friend reappears clearly traumatized.
The Many Worlds Interpretation: The Caltech physicists, both theoretical and research, are keen to explore questions of how the Big Bang happened that created the Universe. Ponder Stibbons and Johanna Smith-Rhodes both know the secret. In fact, they've met the man who initiated the Big Bang - Dean Henry of Unseen University, who put his hand into raw firmament and "wiggled it about a bit just to see what happened". But as the Ultimate Truth is so embarrassing, both conspire not to let the Caltech gang, especially Sheldon, know the awful reality.
- The story also expands a scene from TBBT, where Leonard fires up a hologram of the world to delight Penny, and speculates it might all just be a gigantic hologram being monitored by beings standing outside our Universe, maybe a long-term experiment. Which is nearer to the truth than Leonard could imagine. especially when people from the society that created the Roundworld Universe, and keep it as a long-running experiment they monitor, drop in to check it out on the ground.
- Another recursive reality occurs when, for a brief period of objective time, two versions of Johanna Smith-Rhodes exist on the Discworld as the result of Sheldon Cooper's unwisely applied enthusiasm. Both go around the same time-loop together and this causes double-takes in Ankh-Morpork.
Rick and The Loud House
- Chapter 4 follows the same plot as "M. Night Shaym-Aliens!," with the only difference is that it combines the plot of "No Laughing Matter" in which Luan begins to acknowledge that her family finds her jokes annoying.
- Chapter 19 follows the plot of "The Ricks Must Be Crazy" where Rick must travel into the microverse battery of his car, combined with the plot of "Mall of Duty" where Lincoln must watch over Lily, Lisa, Lola, and Lana at the mall. With the exception of Lily, the siblings decide to join Rick on his adventure in the microverse. Unlike the original episode, where Zeep chooses to continue powering Rick's car so his universe won't be destroyed, Lisa convinces Rick to use Zeep's miniverse in exchange for the teenyverse so he wouldn't have to keep using Zeep's universe anymore.
Tingles Raveng: The Tingling: While My Immortal-style "geddit" pun explanations are a Running Gag in the story, an instance in Chapter 24 has multiple nested pun explanations.

Films — Live-Action

Kaufman's earlier screenplay, Adaptation., is the result of his struggle to write an adaptation of The Orchid Thief, and is about the story of a screenwriter character named Charlie Kaufman, who struggles to write an adaptation of a novel titled The Orchid Thief. The fictional Charlie gives up, too, and writes a screenplay titled Adaptation, which is about, well, you can probably guess...
Charlie Kaufman: (speaking into tape recorder) We open on Charlie Kaufman. Fat, old, bald, repulsive, sitting in a Hollywood restaurant, across from Valerie Thomas, a lovely, statuesque film executive. Kaufman, trying to get a writing assignment, wanting to impress her, sweats profusely. Fat, bald Kaufman paces furiously in his bedroom. He speaks into his hand held tape recorder, and he says: "Charlie Kaufman. Fat, bald, repulsive, old, sits at a Hollywood restaurant with Valerie Thomas..."
Blazing Saddles ends with the heroes going into Grauman's Chinese Theatre to watch...the end of Blazing Saddles!
In Cube 2: Hypercube, Kate at one point opens a door to escape someone who turned murderer, accessing the opposing door from the same room she is already in. Even the madman is a bit baffled at this.
This is the central point of eXistenZ - the protagonists are confused about how many levels of virtual reality Game Within A Game there are, and what they're supposed to do to win. And in the end, they still aren't sure if they're still in the game or not.
The Fountain is a film about a man hunting for the Fountain of Youth. It features the same two characters in three time periods. Given that, you assume they succeed, and Complications Ensue when the girl gets sick and threatens to die on him due to Phlebotinum Failure. But no: the past timeframe is the plot of a book about Tom as a conquistador, told by the dying present day wife, and Tom's character Ascends To A Higher Plane Of Existence in the future timeframe, where he bodily intervenes in the plot of the uncompleted book. Meanwhile, the present Tom does find the Tree of Life, but it's too late to save his wife, and the Tree in question is dying, so he plants another one over her grave where she predicts it will resurrect her as a tree...at the end of the story, the conquistador succeeds in living forever when he stabs the bark of the tree and the immortal tree consumes him. He drops his ring, a a gift from the Spanish Queen, which the future Tom picks up. It turns out to be the wedding ring that the present Tom had lost.
Todd Haynes' Bob Dylan biopic I'm Not There uses a form of this to analyze Dylan's ever-changing personality by having him played by five different actors (and one actress), each of whom's story is depicted in a different genre and visual style. Christian Bale's Bob Dylan expy has his story done in documentary style, and his character was played by Heath Ledger's Dylan in an in-universe Bio Pic. An image of a young Bale appears in a high school yearbook of the Cate Blanchett Dylan, implying that her story is another movie-within-a-movie (or perhaps a drug-induced hallucination), supported by the fact that her segment is shot in the style of Fellini's 8½. Richard Gere, playing Billy the Kid, is antagonized by Pat Garrett, played by the same actor who plays a reporter who harasses Blanchett, implying that the entire story take place within her mind. And that's only four of them... Several of the stories seem to exist within the minds of one Dylan or parallel to the events of another.
Inception has dreams within dreams within dreams (and so on) with time slowing down exponentially with depth, allowing someone to spend decades inside dream worlds. Reached Memetic Mutation where all Recursive Realities henceforth are named with the meme "_____ within a _____. _____ception"
In the movie Last Action Hero, in Jack Slater's universe there are movies where Sylvester Stallone takes up Arnold Schwarzenegger's roles. The main character discovers this in a video store within the movie. It's also shown that the magic ticket stub works just as well on movies within movies, when the bad guy discovers its powers.
Experimental Soviet documentary film Man with a Movie Camera is all about this. The titular man with the camera is shown over and over again, filming the movie. At one point the film stops and reveals still images, because the editor is taking a break. Another sequence shows the editor cutting the footage together, with the resulting footage then playing. At the end an audience assembles in a theater and watches Man with a Movie Camera.
The MacGuffin that draws Edgar Bug to Earth in the first Men in Black film is a miniature galaxy. The final scene reveals that our galaxy is just like the MacGuffin, and lies several layers down within a galaxy-marble that a universe-sized alien on a floating sky island is playing marbles with. (According to the makers, the ending was not meant to be taken literal, as it was simply a gag put in to explain Frank's earlier statement.)
Men in Black II pulls a similar gag by showing a world inside a locker where K's watch is a symbol of worship, then at the end, K shows J that their world is also simply inside a larger locker (doesn't work quite as well as the first film, the moment you think about it). An alternate ending has J going on vacation and ending up on the world inside the locker, being the size of its inhabitants, which implies that either there is some sort of change in size when you go through the locker door, or that the lockers are more of a Portal Network.
The short films Room 8 and Doodlebug explore the idea of recursive realities.
Rainer Werner Fassbinder adapted Daniel F. Galouye's 1964 novel Simulacron-3 into the German movie World on a Wire (a.k.a. Welt am Draht). The protagonist maintains a computer simulation of a whole city. After strange events happening in the real world, it is revealed that the real world is also just a computer simulation constructed in a higher plane of existence. The movie was released in 1973, so is possibly the first film to adapt this trope. Simulacron-3 was also adapted into the 1999 American film The Thirteenth Floor.
Played for Laughs in Spaceballs, where the villains try to track down the protaganists' location ... by popping in an "instant cassete" of Spaceballs on VHS and fast forwarding to the current point in the movie. However, this just winds up being live footage of Dark Helmet and his crew watching an infinite number of themselves watching themselves.
Dark Helmet: What the hell am I looking at? When does this happen in the movie?
Colonel Sandurz: Now! You're looking at now, sir! Everything that happens now is happening now.
Dark Helmet: What happened to "then"?
Colonel Sandurz: We passed it.
- And after another incomprehensible exchange...
  Dark Helmet: When will "then" be "now"?
  Colonel Sandurz: Soon!
1968 experimental film Symbiopsychotaxiplasm: Take One is about the filming of a (fictional) movie called "Over the Cliff"... and the documentary crew filming that movie... and the second documentary crew filming the first documentary crew.
Charlie Kaufman's directorial debut, Synecdoche, New York, is about a playwright who, as part of his new play, creates a life-size model of New York in a warehouse filled with thousands of actors. This model contains a warehouse, which contains another life-size model of New York, which contains another warehouse...
In The Thirteenth Floor, the scientists are creating a simulation they can download their brains into. But it works both ways, the simulations can upload into the real people Eventually, one of the scientists realizes that their own world is a simulation and people have been downloading themselves into him and his friends. One of the people from the layer above starts to treat him like a person when they realize he's built a new layer of this reality and he gets to upload into the mind of someone in the layer above.

Literature

The Arabian Nights is the Trope Maker for the metafictional version — For example, Scheherazade tells the story of The Fisherman and the Genie, where the fisherman keeps the genie from killing him by telling it The Tale of the Vizier and the Sage Duban, during which the evil vizier tells his king The Tale of the Husband and the Parrot.
- Spoofed by Hungarian writer Frigyes Karinthy who takes it to ridiculous levels.
- The 19th century novel The Manuscript Found in Saragossa has a similar structure — Alphonse van Worden meets, imagines, or reads about a number of colorful characters in intertwining stories, in the course of his journey to Madrid.
A rather famous Russian poem from 1922 Atom, later republished as The world of an electron, by Valery Bryusov starts with "What if those electrons // are worlds with five continents, // arts, knowledge, wars, thrones // and memory of 40 centuries?" The idea seems to have been quite widespread back then.
Subverted in Jorge Luis Borges short story "Averroe's Search": In the last page, Borges realizes that he has broke the Stable Fictional Loop and incurred in an Ontological Paradox.
I felt, on the last page, that my narration was a symbol of the man I was as I wrote it and that, in order to compose that narration, I had to be that man and, in order to be that man, I had to compose that narration, and so on to infinity.
In a story in Bigot Hall by Steve Aylett, the protagonist and his friend go out to a small island in the grounds of his home. The first thing they find is a tiny fence, when they tread on it, and then a model of the hall, including a little lake with another, even smaller model of the hall, which has a tiny lake with tiny model...and at this point they freak out, fearing that if look up they'll see giants above them. His father finds them later (hiding under a tarpaulin), and says he knew they were out out on the island when he saw that part of the fence had been flattened.
In Boneland, Colin and the Watcher are playing out the same issues of loss and trauma, in much the same geological place but separated by up to half a million years in time. Both are struggling to work out what is happening to them according to their conditioning and cultural preconceptions. Alan Garner even hints that this is vitally necessary for both to pass on from their respective traumas and emerge into their own lives again. The key lies in the ancient cave-sculptures noted by Colin, which are a representation of Colin's face as it appeared to the Watcher... possibly the very first act of Magic ever to happen on Alderley Edge.
Toyed with in Diane Duane's The Book of Night with Moon. There's a Prime Reality, but it certainly isn't our Earth, and there's nothing better or worse about a given layer. Those layers closer to the prime reality have rippling effects on the surrounding realities, especially those further down the line, though. Taking a chunk of the biggest Russian doll is bad. Smudging the paint on the smallest might be universe-destroying for the bigger dolls.
Roger Zelazny's The Chronicles of Amber uses this, with Amber (and, it's implied, one location in that world) being the ultimate physical manifestation of an ordered reality. All other worlds are shadows of Amber, or shadows of shadows, or so on recursively... all the way down to pure chaos, near which the worlds are so volatile you can often just walk from one to the next. Then it turns out Amber itself is a reflection of a still deeper world, containing the pattern Oberon created. Then Corwin creates another pattern, and, it's implied, another multiverse. Then it gets complicated.
In C. S. Lewis' The Chronicles of Narnia, when Narnia is destroyed, a whole copy of it is inside a barn - plus a copy of our world. (Or more precisely, the outer Narnia-and-our-world are copies of the Narnia-and-our-world inside the barn.) And when the characters in Narnia go to the apple garden, there's another Narnia inside it, and everything gets more beautiful and real as they go inward.
Cloud Atlas is a series of nested stories, told in different stories, through different mediums (a log book, a screenplay, a spoken story, etc.) which abruptly end part way through as the next story begins. Each of the main characters will at some point actually find the previous story, get to the point where it was cut off, and for one reason or another be unable to finish it either. Only the "center" story is unbroken, and as it finishes the others are picked up again and one by one finished.
The Cyberiad: Fables for a Cybernetic Age (1967) by Stanislaw Lem has a robotic prince trapped in recursive virtual dreams by his Evil Chancellor. Once the prince realises what happened, he panics, and desperately tries to wake up "for real" — and at one point he does, but, thinking in his panic that he is still dreaming, keeps trying, thus falling back into endless recursive dreams forever.
- This happens in a story within a story within a story.
- In one of Lem's The Star Diaries stories, Ijon Tichy visits the scientist, professor Corcoran, who build numbers of electron brains. Those electron brains closed in the chests have consciousness and they are thinking that they are real people. Chests are wired to the device which sends electric signals to those brains' senses imitating perception of the real world. Those brains have no clue about their real situation. Except one, who is called by Corcoran 'his world lunatic'. Because of some world imperfections (such as Deja vu or theory of Seriality), this brain suspected that it is not real and everything is just illusion which is served to him by someone or something. At the end of conversation, professor Corcoran admits, that he is also suspecting that he is not real and surrounded by phantoms, products of false signals sent to his senses and that it is probable that even the creator of this world is also a chest in someone laboratory, and so on and on...
Stephen King's first The Dark Tower book implies that Roland's universe is a Recursive Reality, specifically an atom in a blade of grass in our own universe. Later books muddle this somewhat: The Dark Tower setting is more like a mobius strip of recursion, wherein our world simultaneously contains and is contained within Roland's universe, each being both lesser and greater than the other. The Dark Tower tends to be somewhat insanely metaphysical.
- A later Dark Tower novel, The Wind Through the Keyhole, features a minor Scheherazade variant. As Roland and his Ka-Tet shelter from an intensely cold storm, he tells them a story from his childhood. At a pivotal point in this tale, young Roland tells another character the legend of "The Wind Through the Keyhole." After the legend is over, the story returns to young Roland's adventure, and after this ends, the perspective returns to modern-day Roland and company, who move on from the storm and continue their quest.
The plot of the Bernice Summerfield novel Dead Romance uses this trope for some hardcore Mind Screwery; the protagonist discovers that she is from a Universe-in-a-bottle created by the Time Lords, and the reason her (and by extension, our) universe is so mundane is that the Time Lords didn't have enough material handy to recreate all the crazy aliens that humanity in the "proper" universe seems to run into every week. A visitor from the outside universe is astounded that the Pyramids were actually built by humans instead of Ancient Astronauts, for example.
Greg Egan's Diaspora is a Recursive Reality, beginning with the computer network the posthuman protagonists live in and ending in a more or less endless number of non-euclidean universes.
Discworld
- In the Science Of Discworld novels, the wizards create a "model universe" they christen Roundworld. Roundworld is, of course, our world - which implies that eventually Roundworld will contain an author named Terry Pratchett who will write stories about a Discworld in which wizards create a Roundworld, etc. At the end of the first Science of Discworld, Hex actually states (er, writes) definitively that recursion has in fact occurred.
- In Sourcery, the main characters have to travel across the Circle Sea, and do so in the djinn's lamp being carried by one of the characters, which they still have in their hands inside the lamp. This only works because one of them is carrying the lamp and is moving... because they are inside the lamp being carried. It stops working when the universe realizes what's going on, so they are told not to think it through, leading to one of them doing exactly that...
- And in Equal Rites, Esk stands between two mirrors and marvels at her reflections stretching to infinity... and one of them waves at her. This becomes a plot point in Witches Abroad.
Lawrence Miles's Doctor Who Expanded Universe novels contain frequent references to the "bottle universes". The intent appears to be that the Doctor Who New Adventures universe exists in a bottle in the Eighth Doctor Adventures universe ... and vice versa. Mind Screwy enough on its own, other authors (who believed both book series were in continuity with each other) muddled things even further, eventually establishing it was a Klein bottle, and the universe was inside itself.
The Dresden Files: At one point, Harry made a scale replica of Chicago, with a powerful spell on it. When he uses it, he "enters" the model, and is able to move around it. And through it, he can observe things happening in the real Chicago. One unnerving aspect of the spell is that if he looks up at the sky, he sees the interior of his own basement, and a giant size version of himself concentrating intently on the spell.
In The Enduring Flame Trilogy, Tiercel proposes that the worlds are each nested inside the other like a puzzle box. When "lined up" properly, something can move from one world to the other.
A Soviet story "Engineer Alexeev's Mistake" is about a scientist who created a tiny galaxy orbiting Earth. When some time later he decides to shut it down, it turns out that due to time passing differently there, the galaxy has already developed an advanced civilization (with a communistic government, naturally), and managed to retaliate by putting the scientist in stasis.
There is a story called "Fessenden's Worlds" by Edmond Hamilton, where a scientist creates a miniature galaxy to experiment upon. After he's killed (along with the galaxy), a friend of his, who saw it all, keeps thinking "is there a Fessenden out there"?
Flatland contains Lineland inside it, which contains Pointland inside it. It is itself contained in Spaceland, which may be contained in a higher dimension. So, while there are only 2 recursions inward, there may be an infinite amount outward.
A very wide variety of examples can be found in Douglas Hofstadter's book Gödel, Escher, Bach: an Eternal Golden Braid, in which recursion and self-reference, particularly applied to mathematical proof about the nature of mathematical proof, are major themes.
The first part of the classic novel Gulliver's Travels features Gulliver going to the island of the Liliputians whom he is a giant to. The second part has him go to an island of giants that are just as big to him as he was to the Liliputians.
One of the oldest Science Fiction examples is He Who Shrank by Henry Hasse, originally printed in 1936 in Amazing Stories. The protagonist is injected with a serum that causes him to shrink smaller than an atom, where he discovers that every atom is a solar system, with a nucleus for a sun and electrons that orbit like planets. He shrinks through several universes until he lands on our world, and tells his story to a writer who unsuccessfully tries to sell the story to a newspaper as nonfiction.
- Also Science Marched On eleven years before the story saw print - quantum mechanics began to supersede the Bohr-Sommerfeld orbital model as early as 1925, although the Bohr model is still taught today because 1. it accurately predicts the behavior of hydrogen atoms and 2. ease of depiction (subsequent models are heavy on equations and don't actually look like anything.)
- One of the Choose Your Own Adventure books did that too, but with quarks as universes.
House of Leaves is about Johnny Truant, who's editing Zampanó's manuscript about a documentary made by Will Navidson. Neither the documentary nor Will Navidson exist in Johnny's universe, and they may or may not exist in Zampanó's universe. This is the most simplified description possible.
In the John Crowley novel Little, Big: or, The Fairies' Parliament, the world of the Fae is smaller than the human world and exists in cracks and crevices of the latter. By the time a slow-motion End of an Age comes around, the Fae have abandoned their world, apparently for another, smaller one, and the few humans aware of the Fae have taken their places in the Fae world. The further in you go, the bigger it gets.
In the short story "Love Comes to the Middleman" by Marc Laidlaw, the protagonist lives in a house built into a wall of one of the rooms in the house of a giant woman... and all his rooms likewise include the houses of small people, one of whom mentions to him that the same is true of their own house. He later meets a woman (of his own size) who tells him that the house containing the room in which their houses are, is itself in a room of an even bigger house. The progression is implied to be infinite in both directions.
In The Opal, a king receives a magical ring containing his own star. It shows him a planet of incredible beauty, so he spends all the time there, with a beautiful girl, to the exclusion of all else. Later, he exchanges the ring for a kiss from the girl, with her promising to use the ring in order to visit him in turn. By the end of the story, she is yet to follow up on the promise.
The Phantom Tollbooth has the location of the number Infinity.
The Mathemagician stopped what he was doing and explained simply, "Why, in a box that's so small you can't see it—and that's kept in a drawer that's so small you can't see it, in a dresser that's so small you can't see it, in a house that's so small you can't see it, on a street that's so small you can't see it, in a city that's so small you can't see it, which is part of a country that's so small you can't see it, in a world that's so small you can't see it."
Then he sat down, fanned himself with a handkerchief, and continued. "Then, of course, we keep the whole thing in another box that's so small you can't see it—and, if you follow me, I'll show you where to find it."
Philip K. Dick used this in several works:
- In Ubik: The Stinger indicates that Runciter is in a deep-freeze afterlife just like the main cast was, and there's another version of Joe Chip feeding things down to him just like he fed things down to the "dead" Joe Chip. And Here We Go Again!...
- In The Three Stigmata of Palmer Eldritch, it's an article of faith among many Martian colonists that the drug Can-D does this, rather than merely causing shared hallucinations, as most non-users believe. Things get much more ambiguous when Eldritch brings an alien drug, Chew-Z, back from the Prox system.
- The Man in the High Castle ends with the characters, who are all living in an Alternate History where the Nazis won the Second World War, learning from the i Ching that the world they exist in isn't real, that the Nazis actually lost the war, and that the novel that one of the characters wrote about a world where the Nazis lost the war is actually reality. This causes them much confusion. They are, of course, fictional characters in a novel written in a world where the Nazis lost the Second World War, but this isn't the real brainscrew. The real brainscrew is that the world within the book within the book where the Nazis lost the war, which is supposedly reality, is nothing like the world we live in.
The Australian picture book Puzzle Worlds is based on this. A gaggle of hapless airline passengers find themselves in a world inside a well in a town on a flea on a zoo animal... and various nested worlds inside that.
Brian Aldiss' Report on Probability A presents a circular sequence of worlds. Mrs. Mary is being watched by her three servants, G, S and C, who are being watched by some aliens from a parallel universe, who are being watched by scientists observing a rift in reality on the top of a hill, who are being watched by... until we come to the observers in the "outermost" reality, who turn out to be the figures in a painting in the cafe that G, S and C frequent.
One of the simpler examples, the Total Perspective Vortex that Zaphod confronts in Douglas Adams' The Restaurant at the End of the Universe is a model within a pocket universe within "the real thing".
Augustus De Morgan's 1915 comic poem "Siphonaptera" describes an infinite chain of parasitism made of ever larger and ever smaller fleas.
Great fleas have little fleas upon their backs to bite 'em,
And little fleas have lesser fleas, and so ad infinitum.
And the great fleas themselves, in turn, have greater fleas to go on;
While these again have greater still, and greater still, and so on.
Sea of Tranquility: Zoey and her branch of the Time Police are trying to find out if reality exists in a simulation, and hypothesize that a spatiotemporal anomaly that seemed to recur in the 19th, 21st, and 23rd centuries is similar to a file corruption. It's a Stable Time Loop instead... and Gaspery eventually decides that it doesn't matter if reality isn't real as long as one is able to live a good, full life.
In Jostein Gaarder's Sofie's World, Sofie and Alberto break out of their fictional world, written by Albert Knag, into the "real" world... Which is, of course, also fictional, since it was written by Jostein Gaarder. And who knows how many more layers there might be...?
In Jasper Fforde's Thursday Next novels, all the worlds of literature exist in a parallel multiverse called the Bookworld. First Among Sequels features two fictional versions of Thursday herself. If you think about it the books they come from must contain another version of the Bookworld itself.
- At the end, Thursday observes the remaking of the first Thursday Next book. The "on-stage" part is cut-and-pasted from The Eyre Affair.
- And, of course, the "Outworld" - the real world that Thursday comes from - is a fictional world written by Jasper Fforde. She doesn't think so, but occasionally something happens to make her wonder.
Worlds Apart by Richard Cowper. It begins with Universe A being a story in Universe B and vice versa. And that's just the beginning of the Mind Screw, when the universes begin to interact...
The World Inside A Pillow: When Lu sleeps on a porcelain pillow, he is shrunk down, and finds himself getting back to his own home when going inside the pillow.
In Piers Anthony's Xanth series, Princess Ida has a tiny moon the size of a baseball that orbits around her. The moon contains a whole world with its own Ida, and that Ida has a moon with a different world on it, but that moon also has an Ida, who has a moon and so on and so on and so on. Faun And Games was about exploring these moons, and the main character goes through at least six layers.
- In the following book, and in many others beyond, they learn of more and more moons in the line, though past Fractal (#16) the sequence gets murky. In Air Apparent, it turns out there is in fact a finite number of moons, and it is possible to cycle through them all the way to Earth, and now it is possible to go back to Xanth in the same fashion.

Live-Action TV

America's Funniest Home Videos has a clip of a family's dog reacting to the show. Later, a different family sent in a clip of their dog reacting to that dog reacting to AFV. Even later, the family that sent in the first clip sent in a clip of their dog reacting to the other dog reacting to itself reacting to AFV.
Bones is loosely based on a series of novels by Kathy Reichs. The titular Dr. Brennan is loosely based on a younger version of Reichs herself. Both versions are forensic anthropologists, like Reichs, but only the TV version is the successful writer of a series of novels featuring forensic anthropologist Kathy Reichs. Instead of her the novels being loosely adapted into a television series on FOX, there's eventually a movie in the works (with an even younger, sexier, more action-oriented plot). No word yet on whether Reichs' Brennans' Reichs will have written any books.
Community:
- Abed tries to do this via a film project. It doesn't work.
  Shirley: I'm reacting the way the world does to movies about making movies about making movies! I mean come on, Charlie Kaufman, some of us have work in the morning, damn!
- In "History 101", Abed has trouble facing the last year of classes, so he retreats to his Happy Place, a stereotypical sitcom version of the show complete with Laugh Track. Then when things start changing there, he retreats to a second happy place, a cartoon called Greendale Babies. So to recap, Abed has a happy place within his happy place.
In Cosmos: A Personal Voyage, Carl Sagan speculates that our universe could be the equivalent of a subatomic particle inside a "far grander universe we can never see".
In Devs, the major secret project of the Devs team is a simulation of reality itself through which perfect projections of past and future events can be made. By necessity, this means that it must contain a simulation of itself which, in turn, would contain a simulation of itself and so on. This is actually noted as a problem early on — but when it is solved, the resulting implications heavily disturb several members of the team.
Doctor Who:
- "Castrovalva" features a variation on this; the entire town of Castrovalva has been warped in on itself. One of the cliffhangers has a hilarious line from the Fifth Doctor. Doctor:
  Recursive occlusion! Someone's manipulating Castrovalva!
  We're caught in a space-time trap!^TriviaThe deliberately over-the-top delivery of that line was lampshaded in the "Castrovalva" commentary when Peter Davison described it as "end-of-episode acting".
- The entire premise of "Amy's Choice" is a choice between two possible realities in which they keep falling asleep and "dreaming" of the other world, in which they are entirely convinced they are in the "real world" again. It turns out that both scenarios are dreams, but there is a brief moment that could be an Up the Real Rabbit Hole situation.
- Then there's the TARDIS ending up inside the TARDIS in "Time".
The [adult swim] short film Final Deployment 4: Queen Battle Walkthrough starts out like a gaming stream walkthrough of the fictional first-person shooter Final Deployment 4. Then it gets weird. Then the recursion starts: the streamer himself is revealed to be a character in a game played by a female streamer. Then the film focuses back upon the Final Desployment 4 walkthrough, wherein the game is revealed to have a game-within-a-game and an objective is for the character to start creating a streaming walkthrough. In that game is another game-within-a-game. This actually goes for several layers until one of the games features an in-game option to stream... the aforementioned female streamer who was streaming the Final Deployment 4 streamer. That still is not the end of it.
It's Okay to Not Be Okay: In the first episode, Gang-tae and his buddy Jo are pushing Jo's crappy old bicycle across a bridge. They pass a billboard advertising the new Korean Drama It's Okay to Not Be Okay.
In Mork & Mindy, Mork once shrinks down to microscopic size and ends up in an alternate world.
In one episode of MythQuest, Alex gets into a myth by touching a reflection of himself in a mirror in the portal. When he touches the mirror to get back to his world, he actually gets back to a version of his world that isn't quite right. He has to touch the mirror again to get to the real version of his world.
In the Star Trek: Deep Space Nine episode "Far Beyond the Stars", the events of the series are suggested to be a story written by a 1950s sci-fi author named Benny Russell, who is struggling to get his story told on account of having a black protagonist in an era where African-Americans were heavily repressed. This is later revealed to be a vision from the Prophets. The Pah-wraith brings back this vision in "Shadows and Symbols", showing Russell in an asylum writing his stories on the walls as doctors try to convince him to stop, so that Benjamin Sisko would not open the Orb of the Emissary.
In the Star Trek: The Next Generation episode "Ship in a Bottle", the Professor Moriarty created on the holodeck to outwit Data demands that the Enterprise crew work to transfer him into their world. Data later discovers that Moriarty appears to exist outside the holodeck because he actually exits the holodeck on an Enterprise he created within the holodeck on the "real" Enterprise. They make Moriarty think he receives what he wants by transporting him to the simulated holodeck, which runs a simulation of the Enterprise's shuttle bay that makes it seem as if he and his companion are free to explore the universe. As if that wasn't headache inducing enough, Picard wonders aloud whether "All this might just be an elaborate simulation running inside a little device sitting on someone's table". After he leaves the room, Barclay nervously says "Computer, end program." The episode ends there.
The Twilight Zone (2002): In the episode "The Pool Guy", Richie Almares, the titular pool cleaner, continues living the same day over and over, each 'loop' ends with a man saying "wake up" and shooting him. He then wakes up in bed and starts the day all over again, unable to avoid the same ending each time. He spends the episode trying to figure out if he's trapped in a nightmare within a nightmare, a time loop, or a malfunctioning virtual reality experiment. The ending reveals it's actually all three; he's a murderer who is being forced to virtually relive his crime over and over as a form of punishment. The man with the gun was his victim.
Despite multiple concrete examples of crossovers that put Victorious, Drake & Josh, iCarly and Zoey 101 in the same Nick Verse, Victorious as part of one episode refers to Drake & Josh as a TV show.

Music

The booklet for Aerosmith's Nine Lives started as this: the cover with a "cat krishna" fighting snakes was inside a picture with threatening fish, which was in a fish tank, and so on until a picture with caricatures of the band. Then the picture was found insensitive to Hindu religion, and the replacement had a cat person strapped to a wheel, wearing a shirt with the illustration with the Aerosmith caricatures... and then in the fish art, it had the cover, making the recursion circular as well.◊
In The Beatles song "Paperback Writer," the singer tells a publisher that he wants to write paperback books, and that he has just written a book about... a man who wants to write paperback books.
The video of Björk song "Bachelorette" is this in spades (especially so as it was made by Michel Gondry). After finding a book in a forest, which begins authoring the protagonist's thoughts, Björk's character gets it published, gets a theatre adaptation, and then begins acting out the story. When the play hits the adaptation part, the show then becomes a play-within-a-play, and continues looping into itself. In the end, everyone turns into plants for some reason, which ends up burying the book again.
Genesis' "One For the Vine" is about a charismatic warlord about to lead his tribe into battle. One of those who don't believe in him deserts, and flees up a distant mountain, only to slip and fall into a strange valley... where he encounters a tribe who hail him as their new warlord. To his horror, he realises that he is back in the situation from which he was trying to escape. The song ends with him leading his new tribe into battle — and seeing a deserter flee up a distant slope, only to slip and fall...
The Trippy experience that Marilyn Manson gave with "Deep Six" included Manson creeping out of his own mouth over and over again with "LOVE is EVOL, CON is CONFIDENCE, EROS is SORE, SIN is SINCERE" playing over and over until the chorus finally hit again.
The video to Peter Gabriel's ''Steam'' begins with the view of space and stars with Earth closing in and ends with zooming in on somebody's skin, brief glimpse of cellular structure, DNA, individual atoms and interatomic space which becomes the interstellar space again.
The cover of the Pink Floyd album Ummagumma is a photo in which a variation on the same photo is hanging on the wall, which itself contains a variation on the photo and so on in a modified Droste Effect.
Terry Fell & The Fellers, a Country Music group from The '50s, recorded the enduringly popular "Truck Drivin' Man", which is about a trucker who hears a song on a truck stop jukebox called "Truck Drivin' Man".

Pinballs

Both Deadpool tables feature this trope.
- The Deadpool Digital Pinball Table made by Zen Studios appears to recurse infinitely if you pull back the camera. Deadpool plays a miniature version of the table on the left apron, and it appears that you're playing it on the left apron of an even bigger version of the table.
- The Deadpool Physical Pinball Table made by Stern, when no modes are running, shows Deadpool playing the table itself on the main display.
Williams Electronics' Tales of the Arabian Nights requires the player to venture into seven of the Tales and retrieve a magic jewel from each one. One of these is "The Tale of Scheherazade", who is the narrator of the Arabian Nights...

Puppet Shows

The Alice Cooper episode of The Muppet Show had the "Toothache All Over My Body" skit. It starts out with a room full of what look like stalactites and stalagmites. One complains about a toothache that was so bad, it felt like having "toothache all over my body", and the others repeat what he says, and at one point beating him to it, which he lampshades. Then the camera zooms out to reveal that the talking stalactites and stalagmites were all teeth of another stalagmite which is ALSO complaining about a toothache.

Radio

Quiet, Please (1947): "The Man Who Stole A Planet" has an archaeologist finding an old Mayan underground chamber with an inscription saying "The place where the world lives." Inside he finds a little silver globe the size of a baseball, which is an accurate rendition of the Earth. Only it turns out that it is the Earth. When the man flicks a little bit of water on the northern Africa part of the globe, the radio broadcasts a report of cataclysmic rainfall and flooding in the Sahara Desert. When the man pokes Minnesota on the globe with a needle, the radio broadcasts a second report of a massive earthquake in Minnesota. This raises the question of whether there's a very very very tiny man somewhere on the baseball-sized globe, possibly with a little silver globe of his own.

Tabletop Games

The farming board game Agricola features several different "Room" tiles, in one of which a game of Agricola is being played (a few posts down here).
Haunt #99 of Betrayal at House on the Hill involves your party being sucked into a box which is basically a copy of the game you're currently playing without explicitly saying it is, making the players completely rebuild a new house map and play through it within 30 real-world minutes. And if you're really unlucky, you might end up triggering a new Haunt within the one you're currently trapped in...
- What actually happens is when you trigger a haunt in the recursive game is you get sucked into another recursion, only this time with half the starting time of the last instance. And this plays out until the players retrieve the Omen that started the haunt, or run out of time.
One of the Activity cards in the card game Chez Geek is a "Stupid Card Game", and the art for the card is a bunch of geeks playing a game of... Chez Geek.
One campaign for The Dark Eye featured a pocket dimension containing an archipelago on whose islands certain legends were true. One suggested subplot depended on one character dying there; their soul would be transported to, and be able to have encounters in, another dimension while the rest of the group was supposed to find a way to bring them back. (This is not the norm in this game system; mostly, dead means dead.) It was mentioned that if the soul was swallowed by a certain kind of monster, it would be thrown into a realm even further removed, from which they could not be brought back.
The 1st Edition Dungeons & Dragons modules I6: Ravenloft and I10: The House on Gryphon Hill could be played either as stand-alone adventures, as an adventure and its sequel, or as interlocked adventures in which PCs who retired for the night in one module would wake up in the other, and vice versa. This last option could be played as a recurring It Was All Just A Dream, as a recursive Dream Within a Dream, or as the result of genuine shifts between realities.
Malfeas in Exalted. When the Exalted overthrew the Primordials, they needed some way to imprison titanic beings the size of mountains and planets somewhere far away from Creation. Their solution: turn them all inside-out; imprison Malfeas, the Demon City inside the body of Cecylene, the Endless Desert; then imprison all the other Primordials, including Cecylene, inside the body of Malfeas; finally, boot them out of Creation into a separate dimension. Even this was considered too insecure for one Primordial, who ended up imprisoned inside his own wings. Understandably, they're a bit miffed.
Magic: The Gathering allows for subgames, which are games played inside the main game. These have always been part of card effects that end up rewarding the winner or rewarding the loser. There's nothing stopping an effect from creating a subgame in the middle of a subgame, and ad infinitum. The card that allowed this was banned for Game-Breaking (or, more specifically, making tournament matches unending), and all new cards that involve subgames are relegated to tournament-illegal Un-Sets, which sell themselves on breaking all manner of game rules.
One adventure for the appropriately-named Over the Edge suggests that the gamemaster swipe a small item off the table that the players will miss but not worry too much about. The object then shows up in the game world and proves to not quite follow the laws of physics. This can potentially escalate to the player characters arguing with the players.
The Splinter is of the Russian Nesting Doll variety. Earthside scientists created the Realm as a computer simulation, and then the Pyx created their own universe from within the Realm.

Theatre

The Romanian play Jonah is about a man trying to cut himself out of the stomach of a fish, only to find that said fish has been swallowed by another fish. In the end, he finally realises that the whole world is made of fishes, and he just wasted his entire life trying to escape, instead of living normally.
The final scenes of the play Stones in His Pockets concern the main characters trying to get producers to look at a script they wrote, called "Stones in His Pockets."
A Strange Loop: This play is about an aspiring playwright, Usher, who is trying to figure out how to write his play, A Strange Loop. His thoughts (represented by a Greek Chorus) comment on the action, mostly in the negative.
[title of show] is a musical about two guys writing a musical about two guys writing a musical.
- "A, D, D, D, D, F-sharp, A... will be the first notes of our show..."

Video Games

Accounting, a virtual reality game for PC, begins with the player character starting a job as an accountant, and being instructed to put on an in-game VR helmet to access the accounting software. Doing so instead places the player in a simulation of a forest clearing containing, among other things, another VR helmet; it turns out to be the first of an entire series of nested VR environments, each of which contains a helmet that can be used to access the next (and none of which is the elusive accounting software).
- Accounting+, the Updated Re-release for PlayStation 4, can take it even further if you enter a secret level: the VR helmet in that level leads you to a copy of the entire Accounting game, starting from the beginning.
AI: The Somnium Files - nirvanA Initiative: The Naixatloz cult believes that their world is a simulation, and their goal is to escape from it. However, they also acknowledge that it is likely that whatever world they escape to may very well be another layer of simulation, which in itself is within another simulation, and so on. In the final ending, Tokiko does manage to create a tear and leave the simulation, but since this obviously doesn't cause her to physically pop out of whatever device you're playing on, this means that the world she escaped to is still on a lower level of simulation than ours.
In Assassin's Creed: Revelations, Desmond is in the Animus living Ezio's memories, who uses the Masyaf Keys to live Altair's memories.
- And Assassin's Creed IV: Black Flag implies that the reason Desmond himself is in third-person is because someone else is reliving his memories through the Animus.
Baba Is You features a world map that, alongside its own set of levels, contains several sub-maps that themselves contain more levels. After completing enough puzzles, you can access a few levels that can be turned into Baba and a Flag, and then beat the world map and discover that the world map is itself a level on another map above that.
Build-A-Bear Workshop: A Friend Fur All Seasons: Bearemy appears in each Auto-Pilot Tutorial to demonstrate how to hold and move the Wii remote as he plays with his own copy of the game.
The main character of Clash at Demonhead expresses his desire to have a video game made of his adventure during the ending.
Cocoon revolves around an insectoid protagonist exploring and carrying worlds that exist within orbs and has to navigate them in order to solve puzzles and the larger mysteries that surround the game's setting. It gets more elaborate as the game progresses to the point that orbs need to be placed in certain spots and exit pads must be used to emerge from that orb, which is treated as its own reality, to move forward.
Conway's Game of Life allows for the construction of unit cells, which are large patterns that themselves simulate the Game of Life (or any other cellular automaton, if you so desire). As this video shows (albeit with some clever editing), you can theoretically simulate a unit cell with unit cells, and so on.
This is mentioned in one of the "news" feeds in Cookie Clicker when the player has advanced far enough.
"The universe pretty much loops on itself," suggests researcher; "it's cookies all the way down."
In The Darkside Detective, McQueen finds a photograph while exploring an eldritch location, which he describes as showing you, the player, playing a video game in which a man in a trench coat is looking at a photograph.
This comes up in the Updated Re-release of Doki Doki Literature Club! The original game's plot is based around the twist that characters in it can become aware of being Trapped in TV Land and start interacting with the game as a game and involving the real world and the player in the events. DDLC Plus! is compatible with multiple platforms, and because the player needs to be able to interact with the game files at some point in a way that was designed for the PC, it comes with its own interface outside the game proper that seems like some weird custom operating system. You can eventually glean hints that this interface is supposed to be that used by some group of people who are experimenting with sentient and sapient artificial intelligences in a virtual environment, thus explaining how the characters can become Medium Aware. However, it's also implied that these people, whoever the heck they are, also suspect they are trapped in a simulation, and that's why they're experimenting with this kind of thing. It's even more of a Mind Screw because the original story that this was just a romance game you (yes, you, not some character) bought from Steam or whatever is still strongly present and contradicts the simulation explanation, so its kind of like branches and puts the game's reality both one and two(?) steps away from yours at the same time.
One of the pick-ups in Duke Nukem II is a copy of the game on floppy disk.
In Fallout 3, this is the basis of the Church of Atom, a cult that worships the "creative" power of nuclear bombs—they believe that every atom is an entire universe and the splitting of atoms equals the birth of whole new universes and, well, just don't let them near your nukes.
- Nobody ever explains fusion bombs to these people. It might spark a holy war.
This is the entire premise of VR puzzle game A Fisherman's Tale.
The Interactive Fiction game For A Change incorporates this into one of its puzzles. You can find a scale model of your surroundings in a tower. In order to remove a wall that's blocking you in the overworld, you need to find a way to break the corresponding wall in the model. Later on, you need to prevent a flood by finding a way to remove the water from the model.
In Kingdom of Loathing, part of a side-quest introduced as a cross-promotion for the MC Frontalot album Zero Day involves shrinking down and fighting scabies (skin mites) on your own leg.
- The Crimbo 2010 event lets you work in an office that gradually increases your Boredom. Get it too high and you might face the Tome of Tropes, get it to 100% and your character starts playing the Best Game Ever.
Knights of Pen and Paper is a video game about a bunch of real life tabletop players playing a tabletop game. Then one of the main villains invades the real world, materializing in the room the game is being played in, and the players have to fend him off. As their own characters, still using RPG mechanics, with the DM acting like it's still part of the campaign. And then later on the player characters discover a portal back in the game that takes them back to their neighborhood in the real world to fight monsters that have started materializing, still as their own characters, using RPG mechanics, and still just part of the DM's campaign.
The remake of La-Mulana has the protagonist use various pieces of software to aid him in the game. One of those is titled lamulana.exe, and its description is: "Nigoro's first full-fledged game. You're playing it right now!"
Life Is Strange: Max uses her photo-hopping ability to go back to a previous point in time in the Dark Room, when Jefferson was photographing her and she was conscious. From there, she uses the selfie she took on Monday in Jefferson’s class to go back to that point in time and tip off David about Jefferson. A past within a past. Max herself wonders if this is pushing it too far.
In Luigi's Mansion: Dark Moon, there is one room in the second mansion (don't forget, this is a Haunted House) with a dollhouse with windows you can look through. If you do so, you see the very room that contains the dollhouse, with Luigi looking through the window. The one difference is, one of the boxes in the scene you see is shaking. When you stop looking in the dollhouse, that box in the actual room is the one you have to look in to find the ghost that is hiding.
External Gazer, one of the "Snake Tales" included as a bonus in Metal Gear Solid 2: Substance, revolves around the use of the virtual reality system that is the in-universe explanation of the "VR Missions". It turns out that not only does it work by locating a parallel universe matching the training scenario and projecting the user's consciousness into the appropriate inhabitant of that universe, it's also possible for the "simulations" to be nested. Plus, they're nested such that the player must exit the nested simulation as though exiting that component of the game itself. It pretty much bends the fourth wall into the shape of a Klein bottle.
Maquette is a puzzle video game built around this trope. You place objects in a scale model version of the game world to cause a giant version of the object to appear in the overworld, which lets you move objects to otherwise-unreachable places and access new areas.
In Minecraft there are people who have built working computers in the game itself. It has been speculated how long it will take until we're playing Minecraft in Minecraft.
Old adventure game Nippon Safes Inc. has this as one of its examples of meta-humor. In Matsushita Labs Dino finds a pirated floppy disk of Nippon Safes Inc. and makes a little speech on why Digital Piracy Is Evil. In the sequel NSI is apparently still a computer game but it's stated that the event from the previous game actually happened, even if they didn't affect the plot in any meaningful way.
Patrick's Parabox is based around block-pushing puzzles where the blocks themselves can be puzzles. It is possible, and well explored, to put a block inside itself, leading to a recursive puzzle.
At various points throughout the Pokémon games, the player will encounter NPCs who themselves are playing Pokémon.
Psychonauts: The level Waterloo World starts off in a hall where Fred Bonaparte and a mental manifestation of the real Napoleon are playing a board game, from which you can shrink down and travel on an enlarged version of the board game. This allows you to look inside the windows of the prop houses on the board where, in one house, you can find the two Bonapartes playing the board game!
Recursed — if the title didn't give it away already. The game is a puzzle platformer that centers around treasure chests which have rooms in them which can, themselves, have further chests in them, and so on, similar to the above-mentioned Patrick's Parabox. Several levels take this to its logical conclusion, where a room can contain a chest that leads to another copy of the very same room, with another chest that contains another copy and so on. Other levels require you to create such loops yourself in order to solve them.
Saints Row IV. It's made pretty clear from the start that the computer virus-like Dominatrix in the Enter the Dominatrix DLC is a very powerful opponent within the simulation, but it doesn't become fully clear just how powerful until near the end of the DLC when she resets the DLC. Remember: the Framing Device for Enter the Dominatrix is that it's a flashback about the Dominatrix, part of which isn't even set in the simulation. Try not to think too hard about this one.
In SimCity 2000, one of the articles in the in-game newspaper is about schoolchildren learning about city management by playing a Sim City-like game. One of the students interviewed for the article wonders if they're actually just characters in a game like the one they played...
Spaceflux is a First-Person Shooter set in recursive arenas.
Stellaris: Stellaris is set in a multiverse where new universes are born from black holes. Star empires that take the Cosmogenesis Crisis Path acquire a new victory condition. They proceed to perform reckless scientific experiments with galaxy shattering consequences with the ultimate goal of penetrating a black hole's event horizon. Upon success, they enter the baby universe inside the black hole and use Reality Warper tech to redesign it to their liking.
In the final Submachine installment, there is a note of two researchers' discussuion on vertical loops.
We're in a loop.
Yes, I know, there are time anomaly leaks everywhere, but we're not in one right now. Are we?
No, not horizontal loop. Vertical one.
What do you mean?
Look through my microscope. And then through my telescope. You'll see.
<microscope and telescope show virtually the same view>
Superliminal: Some levels contain rooms/portals contained inside themselves, with you changing size as you exit or enter.
In A Super Mario Bros X Thing: Prelude to the Stupid, one level leads the player outside an apartment, inside of which some guy is implied to be doing a Let's Play. The recursion comes from the fact that the game was created specifically for this guy to do a Let's Play of.
- In Make A Good Level X^noteA level designing contest hosted by the forum that did ASMBXT, with the same intention (having it being Let's Played by raocow), but which got so many entries that it actually got its own hub level, the arcade in the Hub Level has two arcade machines which are being played by other characters. One of them is Make A Good Level X, which is being played by raocow.^noteThe other one was A Second Mario Bros X Thing, which is being played by its own main character.
The Stinger of Super Mario Galaxy 2 (which is shown after defeating Bowser in the final level for the second time), actually reveals that the game's events are all part of a storybook Rosalina was reading to the Lumas. While Mario and Yoshi are both flying through space rescuing Peach and the Power Stars from Bowser. And then Rosalina writes herself into her own story about the game where she gives Mario the final Power Star.
The Talos Principle: One terminal document is an e-mail from Alexandra Drennan explaining to the IAN team her idea of creating the simulation. This e-mail includes some hex codes, which when translated to ASCII indicate that the game engine the simulation is based upon is the "Serious Engine 7.5, which Croteam have kindly made available to us." The Talos Principle was made using Croteam's Serious Engine 4.
Time Fcuk: If you press the button to restart the level, your character takes a pill which makes his head explode. However, doing this in the final level gives you the bad ending: When his head explodes, another, smaller version of himself pops out. He proceeds to take a pill and make his head explode. An even tinier him comes out and pops another pill...
In the Sierra point-and-click game Torin's Passage, the worlds are all physically nested within each other, and accessible through warp gates called Phenocrysts. The worlds all have their own atmosphere and sun except The Null Void, so it's not clear if the worlds exist within the same dimension.
This is part of the plot of Imperishable Night, the eighth game in the Touhou Project series. In order to avoid discovery emissaries from the Moon, lunarian refugee Eirin Yagokoro hides the Earth in a magic pot with a fake sky on the inside. She then hides the pot in her home of Eientei. Which is on Earth. Which is hidden in the magic pot.
This is how vivid/stasis's World Axis works, with endless layers of reality, with lower metalayers viewed as fiction by higher ones. Layer 4 is the one with TV Tropes in it, Layer 3 is where Saturday comes from, and Layer 2 is where the Duskbreaker resides. The Duskbreaker also has layers inside itself, although they work more like admin permissions.

Visual Novels

Anonymous;Code: Gai Institution's GAIA Earth Simulator is a quantum computer data center (QCDC) that can make a perfect replica of the Earth up to other copies of GAIA, allowing the users to see private events they were not present for or see the future. If the user with foresight changes the outcome, the simulation gets outdated and needs to be recalibrated. This is considered a violation of the international law even more serious than Nuclear Weapons Taboo, but other nations are also racing to develop their Earth Simulator, like Vatican's Necro Pilgrimage. This includes the current storyline being inside one GAIA instance, which explains all the supernatural stuff, with characters having infinite "real" them in World Layers above.
YOU and ME and HER:
- Early on, Shinichi picks up a game that copies Aoi's life, and assumes that someone has designed a game after her and she now religiously follows it — he notes that the Crash-Into Hello scene was an exact duplicate of what actually happened. Later, he uses it to see into the future, and after one of the endings he replays the exact copy of the player's experience on top.
- If you punch in the code to force the game to 100% Completion, then You and Me and Her becomes a Game Within a Game that Shinichi has played to 100% completion and is viewing the scenes of out of boredom, with Miyuki and Aoi reduced to even more fictional characters.

Web Animation

One Cyanide and Happiness short involves a couple attending marriage counseling. The counselor suggests using hand puppets for role-playing, and the puppets role-play going to marriage counseling, where they role-play using puppets for role-playing who role-play going to marriage counseling... it ends up many, many layers deep, but this turns out to be an effective way to work through their issues.
The end of the Inside Out episode of How It Should Have Ended has Bing Bong ask Joy if she has little people inside her head (this is while she's crying over a fading memory while stuck in the Memory Pit). Cut to five Joy-shaped emotions inside her head, then cut back to her replying "It's better if you just don't think about that!".
Macrocosm is an animation about a scientist who creates an infinitely-recursive chain of identical realities, only to realize that he is part of the chain himself. It doesn't end well.
The ending of Red vs. Blue: Revelation leaves room for the interpretation that the entirety of the Recollection trilogy is a digital world created by some version of Epsilon where he lives out the rest of his life in a memory (including the part where he created a digital world). Burnie Burns stated in an interview that the setting of The Blood Gulch Chronicles was real, but deliberately left the rest open to debate.

Webcomics

Let's see the Buildingverse (so Roommates, Girls Next Door and Down the Street and their assorted fanwork) is a Megacrossover Meta Fic 'verse, where the (for them) real stories of the characters, are fictional (so all the responsible people exist. James already placed Orlando Bloom as his problem with Legolas), that is fictional in ours, and the cast knows this. This isn't even accounting for all the Dream Within A Dream Lands The Fair Folk can create from the inside, or the possibility for stories being Mutually Fictional, or the ability to travel to the worlds of other fiction (Jareth even managed to "fix" Inception^noteSo according to this there is a missing scene, where he brings forth the canonical ending, because Saito messing with his love interest's dreams from Limbo annoyed him.). And don't let us get started on the implied possibility to read the comics in the comics. Is there a true reality? Does the chain of fictionality ever end? We don't know. You reading this could be fictional in some other world/story too. ... And this isn't a twist ending, this is one of the most basic facts about these comics. Also the authors read each other's work, and some even TV Tropes. So questions, ideas, characters etc. flow kinda free between the worlds making up the 'verse. At the end it's either All Fiction Is Real Somewhere or an exceptionally pretty Butterfly! Or both.
Cochlea & Eustachia has objects (including one of the protagonists) containing entire living rooms complete with furniture and occupants.
Darths & Droids has no film version of Star Wars in its world, with the plots of the movies used for a Tabletop Game instead. In that world, however, there is a webcomic about a world that has no Harry Potter movies, with the plots of those used for a Tabletop Game. The layering goes down and down and down, with another movie added every 50 strips. It gets especially meta with this installment, based on Inception.
Drowtales: One of Kiel'ndia Vel'Vloz'ress' many quirks is her belief in the "infinity turtle".
Chirinide: If the netherworlds aren't populated by demons, then what is it to you!?
Kiel: Turtles.
Chirinide: TURTLES?!
Kiel: Yup, turtles all the way to infinity.
There's a one-off joke in El Goonish Shive where the Author Avatar is actually a character in the comic strip created by Sarah.
- Also there is this sketchbook which features the three original main characters (plus the Goo) viewing the first strip.
Briefly referenced in Freefall. Sam thinks he's found a way past his ship's idiot lock and gotten it flying, but in fact the ship had simply directed him to a flight sim. When he notices, he orders the ship to end all virtual reality simulations... and Helix promptly covers Sam's eyes, causing him to scream.
In Homestuck, the Battlefield, Skaia, is contained in the King's scepter. Said king is fighting on the Battlefield. And there are two kings.
- Every single universe is apparently a giant frog, which is made in the Sburb game session of the previous universe. I.e. Earth C is in a universe that's a giant frog in Earth A and B's universe, which in turn is in a universe that's a giant frog in the Troll's universe, and so on and so on.
- Snowman's heart contains the troll universe, she is currently inside the troll universe.
- Not to mention that The Tumor is a bomb using the death of two universes as a catalyst. The two universes are the Troll universe and the Human universe, both of which are contained within it.
Pyramid-exclusive Irregular Webcomic! #26 features multiply-nested Role-Playing Games.
In Larp Trek, some of the characters in the RPG are future versions of people playing the game, in reference to characters crossing over between Star Trek: The Next Generation and Star Trek: Deep Space Nine.
The page pic is from a The Perry Bible Fellowship strip in which an astronaut somehow lands on his own helmet; when he takes it off he can see a miniature figure of himself standing on it holding a miniature helmet with an even smaller figure of himself standing on it holding...and to make his day even worse, his bald spot is spreading.
xkcd plays with this a few times; see, for example, recursive roleplaying.

Web Originals

Web Videos

Western Animation

Adventure Time:
- "The Real You" has Finn put on some intelligence-boosting glasses, resulting in an Astronomic Zoom on him down to the atomic level, then down to the galactic level, and finally back down to the level of Finn and Jake themselves. It gets reversed when Finn's glasses are removed, ultimately zooming out on his keister.
  Finn: Everything small is just a small version of something big! I understand everything!
- The season 6 episode "The Mountain", where Lemongrab and Finn are seen running on their own respective bodies.
- There is an in-universe Gender Bender fanfiction titled "Fiona and Cake", mostly written by Ice King, but other characters have added to it. Occasionally, there are episodes depicting this. According to the episode "Five Short Tables", the Ice Queen writes genderbending fanfiction called "Flint the Human and Jacques the Raccoon". In that fanfiction, the Ice President writes fanfiction about "Lynn the Person and Janet the Fox".
The song "Yakko's Universe" from Animaniacs had the entire universe turn out to be inside Yakko Warner's snowglobe twice.
In the first episode of Be Cool, Scooby-Doo!, Daphne's Establishing Character Moment is that her first Once per Episode quirk is conversing using hand puppets of herself and the gang. When revealing them, she shows that her puppet of herself is wearing a smaller version of itself, which has a smaller version of itself, and so on.
An episode of Chowder opens with Chowder eating a gumball with muffled screaming being heard as he chews it. At the end of the episode when Chowder has gummed everyone and everything on the planet together, the planet gets eaten by another Chowder and the same screaming is heard.
In the Earthworm Jim episode "The Great Secret of The Universe", the universe is inside a giant snow globe, which is owned by a child as a souvenir.
Futurama:
- In "The Series Has Landed", we see a character in an arcade playing Skeeball. In the next area over, a character is playing Virtual Skeeball; they have on a headset and gloves in an otherwise empty area, and are moving like they're playing Skeeball. Next to them, Amy is playing Virtual Virtual Skeeball; she's sitting on a chair with a headset on, and comments "Wow, I could swear I was really playing Virtual Skeeball".
- In "The Sting", Leela experiences the Dream Within a Dream type. She slowly realizes she's in a dream (or going insane) and keeps trying to escape only to end up in more bizarre situations. She meets Fry each time, who tells her she needs to "wake up". It turns out that she's in a coma, and she's hearing the real Fry (at her bedside) pleading with her to "wake up".
- In "The Farnsworth Parabox", Farnsworth ends up creating a box containing a portal to an alternate universe, the other end of which is a box the alternate Farnsworth created. At the end of the episode, the two Farnsworths somehow manage to trade boxes through the portal, meaning the box "our" Planet Express crew currently have contains their own universe.
Horton Hears a Who! (1970) is about an elephant who hears voices from a tiny town called Who-ville, built on a dust mite. At the end, there's a scene where the main Who hears a voice coming from a Who-scaled dust mite...
An episode of I Am Weasel revolves around Weasel, Baboon and Red Guy trying to find out where everybody in the world has gone to, leaving every public place empty. It turns out everybody is home, watching I Am Weasel. And yes, it DID in fact include a shot of Weasel in front of a TV showing him in front of a TV showing him in front of a TV showing him... To be honest, though, this wasn't even one of the weirdest episodes.
Johnny Test has an episode similar to "He Who Shrank" — Johnny shrinks to smaller than a quark, and it turns out that each quark is an entire universe.
Jorel's Brother: When the titular character gets lice in his head, he finds out his lice also have lice, which also have lice, which also have lice, and so on. In the end of the episode, it's revealed that the characters' world itself is actually the lice of an alien dinosaur.
In the short film The Killing of an Egg, by Paul Driessen, a man hears a voice coming from the soft-boiled egg he is cracking and maliciously crushes it. He then hears knocking outside his house, and finds that he is now the one being crushed.
Rick and Morty:
- In "Lawnmower Dog", Rick and Morty enter the dreams of Morty's math teacher to incept the idea that Morty should get an A in the class. As they wind up in trouble, they escape to the dreams of people in the dreams until they hit "dream bedrock".
- In "M. Night Shaym-Aliens!", Rick, Morty and Jerry are captured by Zigerian scammers and placed in a simulation, inside a simulation, inside of another simulation.
- In "The Ricks Must Be Crazy", Rick builds a battery for his car that contains a tiny universe. In the universe, a sentient species evolves and Rick introduces them to electricity by doing an ancient aliens schtick, and then siphons off their grid to produce real-world electricity. The battery stops working when a Rick-like scientist from that world (played by Stephen Colbert) invents a similar sub-universe battery. There is another scientist in the sub-sub-universe that is working on his own sub-sub-sub-universe.
A sketch in the Ruby Gloom episode "Ubergloom" has Ruby and Scaredy Bat baking a gingerbread house, then hearing their speech repeating from an unknown source. It turns out that the house has a smaller Ruby and Scaredy Bat inside it, who in turn have just made their own gingerbread house and run away in fear upon seeing their larger counterparts, the larger Ruby simply calling the phenomenon strange. It's then revealed that they both dreamed the whole thing as a result of eating gingerbread before bed.
A Couch Gag in The Simpsons begins with a reverse Astronomic Zoom from the Simpsons' couch to outer space, revealing it to be an atom in one of Homer's hairs. Word of Dante says that it was a parody of the 1977 short film Powers of Ten, and that Homer was thinking of it; it was not in an atom in Homer's hair, it was his thoughts.
Homer: ...Wwwwoooow.
This trope is the premise of Rebecca Sugar's short film Singles. The protagonist's apartment exists within his own chest cavity; he's able to reach in and affect the room, or step out into the infinite void.
South Park uses the fourth type for the episode "City on the Edge of Forever". In the end, it turns out that Stan has emotional problems, so he, Kyle, Cartman, and Kenny (who didn't technically die this time) go for ice cream. The end.
SpongeBob SquarePants:
- In "No Free Rides", when Mrs. Puff enters the house during the surprise party held by Spongebob's parents, there's a picture on the wall that depicts the exact same situation of Mrs. Puff entering the house. And there's a picture on the wall as well, which also shows Mrs. Puff entering the house the same way...
- In "Bummer Vacation", SpongeBob is made to go on forced vacation, so he consoles himself with the Official Krusty Krab Playset. Toy-SpongeBob ends up accumulating too much vacation time as well, so he's forced to go on vacation, resulting in Toy-SpongeBob playing with Toy-Toy-SpongeBob and... yeah, the real SpongeBob decided to cut it off there.
- In "Truth or Square", SpongeBob, Patrick, Squidward, and Mr. Krabs go to the Krusty Krab's surveillance room when trying to find a way out of the building's duct system. One of the video feeds they watch is showing them watching the video feed. Then it is revealed that the surveillance room was recorded by two fish who appeared out of nowhere and run away when noticed.
- In "Lost and Found", SpongeBob comes across a snow globe of Bikini Bottom on a shelf while looking for a kid's teddy fish within the Krusty Krab's lost and found. He shakes it once, which causes the whole town to shake violently. He very wisely puts the snow globe back and backs away.
Steven Universe: In the episode "A Single Pale Rose", it is revealed that Pearl's gem contains a world which also has a Pearl with her own world in her gem, repeating for several layers. The Pearl in the surface layer organises the things that outer Pearl stores in her gem and the Pearls in the deeper layers relive Pearl's important memories in reverse order. Steven has to travel though these layers to find Pearl's missing phone after he receives a text message from one of Pearl's inner selves.
Teen Titans (2003):
- One Kids' WB! ad for the show has Robin and Starfire sitting on the couch in front of the TV. Starfire asks Robin what he's watching; he says he's watching Teen Titans. Zoom out to show a recursive image and Starfire asking Robin the same question. They do this enough times to put it barely short of an Overly Long Gag, then Starfire breaks the fourth wall, asking the audience what they're watching.
- In "Nevermore", Cyborg and Beast Boy are sucked into Raven's Magic Mirror, which transports them into her mind. The weird part of this is, Raven herself is somehow able to go there — meaning she's inside her own mind. She doesn't explain how that's possible, and they don't even question it (likely because there's a much bigger problem — Trigon — threatening them). An even weirder part of this is how Raven tells them that they'll be trapped there forever if she's beaten (the reason why she pleads with them to leave). Given that they're inside her mind, it isn't known exactly how it's possible that the place could even still exist if she were killed (assuming that's what she meant by "beaten").
- "Bunny Raven or How to Make a Titananimal Disappear" has the characters being imprisoned by Mumbo in his magic hat. Cyborg points out that Mumbo, appearing in the world inside the hat, is still wearing his hat — which everyone is still inside, including Mumbo, and his hat.
The short film "Zoom"^noteonce shown on Nickelodeon by Istvan Banyai. There's this piano melody, and we see the pianist. Pull out, he's in a bubble, pull out, gets eaten by a fish, which is in a little boy's bathtub, which is in a house, in an apartment block, in a city, on a magazine cover, being read by an Arab on a camel, which is actually on a stamp on an envelope, being delivered by... and on and on until it's all in a little girl's toy city and that damn piano melody stops.

Real Life

Metaphysical

The Turtle Island cosmology is the basis for the famous often-cited "argument" / joke / thought experiment in cosmology and metaphysics known as "Turtles All The Way Down", see that other wiki for details: Man #1:
If Earth is the back of a giant turtle, then
what's holding up
the
turtle?
Man #2:
Don't be a fool. It's Turtles All The Way Down!
Because black holes are believed to contain a singularity point of infinite density, and the similarity of this to the sudden explosion of energy of the Big Bang at the beginning of time, it is possible that all black holes contain a universe, and with countless billions of black holes in this universe, that would lead to an infinite fractal blossoming of universes creating enormous amounts of subsequent universes. This is a popular pop physics theory, but is viewed with considerably more skepticism in the hard sciences, as the hypothesis cannot yet be tested. And hypotheses which cannot be tested also cannot be validated, making them outside the realm of the scientific method.
Philosopher Nick Bostrom has written that if there's ever going to be a recursive simulation of reality, then we're probably in it already. The thinking is that if humanity ever reaches a point where it could have highly detailed simulations of reality and could have amounts of computational power so vast as to be functionally infinite, then because there are likely to be many many more simulated realities, each with their own potential for further simulations, then statistically, reality is more likely to be one of the countless simulations than the few real worlds. The idea is a more refined and technological variation on a topic which has stretched back throughout history, though phrased more as dreams until the advent of computers and the creation of the first virtual worlds. The "simulation hypothesis", as it's commonly referred to, has drawn a lot of criticism from other philosophers and been dismissed by physicists as an untestable hypothesis, yet does have parallels to common theological threads and is believed by many futurists. Of course, materially, very little changes whether the world is a simulation in a computer or a tiny rock hurtling through space.
In case you're worried about the universe exploding by paradox, here's another thing to worry about: does the set of all items that do not belong in a set include the set itself?
- By definition, a set cannot contain itself. This was an Obvious Rule Patch that was made specifically because this case was brought up.
- Early in the 20th-Century, set theory was redefined, automatically avoiding sets containing themselves (or forming loops of containment — indirect recursive containment). A standard version appears to be ZF Set Theory. This may have created new potential recursive paradoxes.

Others

Infinite Fractal Zooms, such as Mandelbrot Sets "Bigger than the known universe!" Turn on the Mood music when watching these... Schpongle perhaps.
- The Mandelbrot set is vaguely turtle-shaped, and the shape reappears no matter how deep you zoom in, so you could say that it is turtles all the way down.
There are any number of magazine covers with a Droste Image — where somebody on the cover is holding a copy of the magazine with the cover that they're in, etc.
- Hell, Games Magazine made a puzzle out of it.
- Numerous commercials have used a similar effect, where a photograph in one scene expands and animates, becoming the ad's next scene. Usually, this also has a photo or other image in it, which also expands and animates...
Raëlians believe that our universe is a tiny particle within the body of a living creature in a much larger universe, and that all atoms in our universe also contain smaller universes similar to the one we live in.
Many things can display recursive images of themselves:
- If you have two mirrors face each other, they reflect their own reflections.
- Hook up a video camera to a monitor and point the camera at the screen.
- Set up a screen-recording program so that its interface displays whatever is being recorded, then leave said interface up so it records itself. Some programs, such as OBS, do this by default.
- Screenshots of a graphics editing program can be pasted back into into the same program.
- "Who cares. Go here. Right-click download and Save as OR you can go over here oh! Can we watch ourselves? Will it let us do that on here OH MY GOD!"
The Internet, perhaps. If nothing else, it can, and possibly should, be seen as a world within a world.
- Thanks to the likes of web archives such as the Wayback Machine, mirrors of specific websites, and backups of individual pieces of content, the Internet also contains incomplete copies of the Internet, making it partially recursive.
- These days, there are many, many social networking websites. To get into it, you typically have to sign up. Those who don't sign up don't see what's happening in those websites. It's thus an internet inside the internet. This is a problem for search engines, who want as much information as possible from everywhere on the internet. Apparently, this "hidden web" phenomenon is disturbing enough for Google that it's criticizing Facebook for exactly that.
- This is true for all "Deep Web" websites and web-content, which is by definition not searchable since search engines cannot find it (Deep Web content is not searchable usually because it requires login credentials, which includes data banks of companies, private citizen information, and the contents of e-mail accounts as accessed via Webmail clients, and also parts of websites that Web crawlers specifically are banned from even though they can be accessed without authentication; this concept is similar to but distinct from darknets, overlay networks such as Tor and I 2 P, on which search engines do exist, but most Web content on darknets is also Deep Web content, inaccessible directly from even darknet-oriented search engines). It is estimated that the Deep Web is at least a quarter the size of the searchable "surface" Web, but by definition it is impossible to know how large it is.
Emulators and virtual machines. VirtualBox, for instance, simulates one PC within another PC; it's great for playing with different mutually incompatible PC operating systems, or for completely isolating applications in one "box" with another. In fact, it's possible to run PocketNES (a Nintendo Entertainment System emulator for Game Boy Advance) inside VisualBoyAdvance (a GBA emulator for PC) inside VirtualBox.
In this video, someone uses the embedded web browser in Second Life (textured to an in-game laptop, no less) to access a remote desktop viewer, which they use to... log into Second Life
There is a gif that shows a spacecraft speeding towards a Death Star-esque surface. But the surface is recursive, so it never actually gets there.
This sometimes happens with model villages, when the model is of the village that contains the model (Godhill on the Isle of Wight being one). In order to properly represent the village, the model must include a model of itself, which should include a model of itself, and so on. The only limit is how tiny the model makers can make the smallest model. If you count the real church, it is possible to see Godhill's church on five scales at the same time.
The Beatles named their last recorded album Abbey Road after the street on which the studio (then called EMI) is located. The studio was consequently renamed "Abbey Road Studios" after the album (the sign above the door is a representation of the album cover).
Recursive islands and lakes are this in a nutshell:
- The Philippines used to have an island that was nested inside of two larger islands. Vulcan Point Island was located in Crater Lake, which was located on Volcano Island, which is located in Taal Lake, which is located on the island of Luzon, which is located in the Pacific Ocean. However, Crater Lake drained in 2020, eliminating the innermost layers.
- Indonesia's Lakes Sidihoni and Aek Natonang are located on Samosir Island, which is located in Lake Toba, which is located on Sumatra Island, which is located in the Pacific Ocean.^noteIt should be noted that Samosir was not originally an island, only becoming one when the Dutch dug up a canal in 1907 that separated it from the rest of Sumatra.
- A few comparable islands-within-islands still exist in the Canadian Arctic.

Uncle Peter's Jug Band

Uncle Peter shows Vic and Bob a jug, inside of which was Uncle Peter's band playing music - including Uncle Peter himself.

Alternative Title(s): Russian Doll World, Matrix Hypothesis, Transfictionality, Turtles All The Way Down

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