%% Image selected per Image Pickin' thread: http://tvtropes.org/pmwiki/posts.php?discussion=1305031190067319400
%% Please do not change or remove without starting a new thread.
%%
[[quoteright:228:[[Webcomic/{{xkcd}} http://static.tvtropes.org/pmwiki/pub/images/mutually_fictional_4153.jpg]]]]

This is a special kind of crossover trope in which the characters from Show A will enter the universe of Show B--both shows of which are "real" to us. In other words, neither is a ShowWithinAShow. In addition to finding out that they're trapped in the universe of Show B, the characters of Show A discover that they themselves are the subject of a Show A in the universe of Show B. The characters from Show A are, in essence, ''simultaneously'' TrappedInTVLand and a RefugeeFromTVLand. This isn't WelcomeToTheRealWorld, since both universes are depicted as being [[UpTheRealRabbitHole equally "real"]].

A situation in which Show A is fictional in Show B and Show B is fictional in Show A isn't an example of this trope if they never share a continuity; if in A's continuity B is just fiction and vice versa. This could happen with two completely unrelated works that each incorporate real world elements that happen to include the other work.

This is a relatively common trope used in {{Crossover}} FanFic.

[[RecursiveCanon Strictly speaking]], this kind of crossover should never [[FridgeLogic logically]] be allowed to exist. At the very least, the particular episode of each series or work [[CelebrityParadox which references the other]] should be assumed to [[RetGone not exist]] [[CanonDiscontinuity within the other's]] [[{{Verse}} universe]]. Otherwise, you would have a situation wherein it would be distinctly possible for the main characters to see the TV show of their entire reality within said reality, [[BrokenMasquerade realize their entire existence was a lie]], and [[HeroicBSOD freak out]]. And we wouldn't want that, now would we?

One possible {{justifi|ed trope}}cation would be if the two worlds are simply {{Alternate Universe}}s and the "shows" in question are [[{{Transfictionality}} based on visions]] people have [[VisionsOfAnotherSelf from the other world]]. In this case, expect the characters trying to establish what in this shows is correct and what is not. Unfortunately, the FictionIdentityPostulate proves that all fiction is equally unreal. And anyone living in an AlternateUniverse may be, by definition, fictional.

This is where RecursiveCanon meets RecursiveReality. May create an accidental IntercontinuityCrossover.

See also CelebrityParadox. ComicBooksAreReal is a one-sided version, usually dealing with a ShowWithinAShow instead of another real-life series. Compare FaeriesDontBelieveInHumansEither, where each side ''believes'' the other is only stories prior to meeting, but both have always been fact and that's what the stories are based on. Contrast StableTimeLoop, which leads to a similar [[OntologicalMystery Ontological Paradox]].

----
!!Examples:

[[foldercontrol]]

[[folder: Anime And Manga ]]

* A ShowWithinAShow example: Many characters in ''MartianSuccessorNadesico'' are fans of ''Gekiganger 3''. The RecapEpisode showed that, in turn, the main characters of ''Gekiganger 3'' are fans of ''Nadesico''.
** [[MindScrew To make it even stranger]], each [[{{Defictionalization}} defictionalized]] something from the other in-verse. Done mutually with [[spoiler:the Gekigan flare]].
* ''Anime/ExcelSaga'' featured a kid who drew forged key frames from the ShowWithinAShow ''Anime/PuniPuniPoemi''. The show was {{Defictionalized}}, and in ''Puni Puni Poemi'', a math problem in school involves the number of cels used in each episode of ''Excel Saga''.

[[/folder]]

[[folder: Comic Books ]]

* Once upon a time, MilestoneComics and DCComics' Comicbook/{{Superman}} [[BatFamilyCrossover books]] participated in a CrisisCrossover, ''Worlds Collide''. The story started with a mailman in the DC Universe who went to sleep and dreamed of waking up and working as a mailman in the Milestone universe (or vice versa), until other strange things started happening in both universes. The ''ComicBook/BloodSyndicate'' (essentially a [[VillainProtagonist streetgang with powers]]) were the first Milestone characters to meet Superman, and although they thought he was just a local wannabe, they all immediately knew who Superman was, what he could do, etc., because Superman was a comic book character in the Milestone 'verse. ("Does your mama know you left the house looking like Clark Kent?!"). Superman doesn't have the same benefits, realistically, since the Milestone Comics characters were hardly a household name, and he's not much of a comic fanboy.
** ComicBook/{{Static}}, an AscendedFanboy, lampshades this; he drops his knowledge of PostCrisis Superboy's history, and explains "I read all your comic books! Don't ''you'' read all of ''my'' comic books? (Do I ''have'' comic books?)"
** In the wake of a CosmicRetcon, the two universes have now been merged with a new, shared history. Only a handful of people (including Superman) remember that they were ever separate.
* This happens to Superman a lot; it used to be that DC/Marvel crossovers operated under the conceit that the characters, if they didn't know of each other, at least operated in the same reality for the duration of the Crossover (Spider-man/Batman, for example), but after ''DC vs. Marvel/Marvel vs. DC'', they were explicitly separate realities. It is true that the Fantastic Four knew of Superman from the events of that crossover in ''Superman/Fantastic Four'', it was also established that Ben Grimm and Franklin Richards knew of Superman from the exploits of his comic book counterpart.
** Incidentally, ''Marvel vs. DC'' played with a retcon of ''Spider-man/Batman'' when the Joker recognized Spider-man from somewhere. Of course, since S/B was set before the Spider-clone saga and ''DC vs. Marvel was set after, Ben Reilly Spider-man didn't recognize the Joker from Peter Parker's adventure.
* Speaking of DC Comics, PreCrisis at least, Earth-One and Earth-Two were fictional to each other, and on [[WelcomeToTheRealWorld Earth-Prime]], supposedly all the other alternate universes were fictional.
* The first ''Futurama/Simpsons'' Bongo Comics crossover comes about as the Brainspawn zapped the Planet Express crew into an old ''Simpsons'' comic. The second has the ''Simpsons'' characters [[spoiler:and later, many other fictional characters]] materialising into the reality of ''Futurama'' from a comic by one of Farnsworth's inventions. However in their Bongo Comics crossovers, TheSimpsons are pointed out as the fictional ones in {{Futurama}}'s "real" universe. It should be only one way, being built off the idea in "The Day the Earth Stood Stupid" where the Brain can take people into worlds of fiction but since Matt Groening cameos on TheSimpsons as the creator of Futurama...
* TerraObscura. Their science heroes are the stars of comic books in ComicBook/TomStrong's world, and vice versa.
* JimmyOlsen in ''{{Superman}}'' comics is a fan of the Spin Doctors, a band with a ''Superman''-inspired album and a song about Jimmy Olsen.

[[/folder]]

[[folder: Fanfiction ]]

* FanFic author Jared "Skysaber" Ornstead used this trope to invert the SelfInsertFic trope of {{Author Avatar}}s knowing everything about the [[TrappedInAnotherWorld worlds they visit]]; there's always a ShowWithinAShow based on his life in each one, and at least one of the characters is guaranteed to be a fan.
* In the ''Literature/HarryPotter'' and ''FateStayNight'' crossover FanFic "Fictional", Harry is a servant created by Caster from the book series. A big part of the plot is Harry coming to terms that all of his hardships were [[TitleDrop fictional]] and how to deal with it after the obligatory freak out. And you know, deal with being a slave (*cough* Servant). He also has to hide his scar, because other people freak out when they meet Harry Potter too.
* FanFic/TheInfiniteLoops actually justifies this trope. The admins responsible for repairing the multiverse store backups of universes wherever they can, which has the side effect of making the natives write fiction about that universe. The Hub universe is simply the most well protected and undamaged area, which is why we have all this fiction....

[[/folder]]

[[folder: Fan Works ]]

* Played with in M. [=McGregor=]'s "[[http://www.tthfanfic.org/Story-16694-62/MMcGregor+The+Wonderland+Subject.htm The Wonderland Subject]]", a dimension-hopping ''Series/BuffyTheVampireSlayer'' / UltimateMarvel crossover in which each universe has fiction based on the other one. Xander and Jean Grey spend quite a while [[TheKnightsWhoSaySquee being fannish at each other]].
* In ''Fanfic/KyonBigDamnHero'', characters make several references to ''LuckyStar'' -- which, in turn, contains many references to ''SuzumiyaHaruhi''.
** It has been [[WildMassGuessing theorised]] that in the fanfic's universe, ''LuckyStar'' references "the JustForFun/TropeTan [[ShowWithinAShow anime]]" instead of ''SuzumiyaHaruhi''.
* Within Series/{{Sherlock}} BBC fanfiction, Series/{{DoctorWho}} has been both fictional (e.g. John Watson's a whovian) and real (e.g. John is the son of Captain Jack Harkness, a character on Doctor Who), depending on what universe the fanfiction author is writing in. Additionally, some Whovian fanfiction features the Sherlock characters as real people, or claims that the Doctor is a fan of the original Conan-Doyle figure. *Cue Rift crack*

[[/folder]]

[[folder: Film ]]

* In the first scene of ''Film/{{Scream 1996}}'', the film ''Film/{{Halloween 1978}}'' is the subject of one of the questions the killer asks, and later ''Halloween'' is shown at a party (with one character [[GenreSavvy loudly protesting at the mistakes Laurie Strode is making]]). Likewise, in the ''Franchise/{{Halloween}}'' sequel, ''Film/HalloweenH20TwentyYearsLater'', a couple of characters are watching ''Film/{{Scream 2}}'' in one scene.
* Also, in ''Film/JayAndSilentBobStrikeBack'', the duo stumbles upon the the filming of a ''Franchise/{{Scream}}'' movie. The first movie in the series had a poster for ''Film/{{Clerks}}'', a movie in [[TheViewAskewniverse the same continuity]] as ''Jay and Silent Bob''.
** Though it's not explicitly stated to be a ''Scream'' film, it could have been a ''[[ShowWithinAShow Stab]]'' movie, as some fans think.
** Made more complicated when Jay and Silent Bob make a cameo in ''Film/{{Scream 3}}''.
* In ''Film/ANightmareOnElmStreet3DreamWarriors'', the TV-obsessed patient is seen watching an early scene from the movie ''{{Critters}}''. Later, ''Critters 2'' had one of its alien doppelgangers attempt to imitate a cardboard Freddy Kruegar standee at a video store.
** In the first ''Film/ANightmareOnElmStreet1984'', ''The Franchise/EvilDead'' is seen on a TV, a ShoutOut to a poster for Creator/WesCraven's earlier film ''Film/TheHillsHaveEyes'' appearing in ''The Franchise/EvilDead'' (which was itself a ShoutOut to a poster for ''Film/{{Jaws}}'' appearing in ''Film/TheHillsHaveEyes''). Then in ''Franchise/EvilDead 2'', Freddy Krueger's glove is seen in the shed where Ash creates his chainsaw-hand. Confused yet?
*** Averted in [[Comicbook/FreddyVsJasonVsAsh the comics]], there was an UltimateShowdownOfUltimateDestiny between Freddy, Ash, and [[Franchise/FridayThe13th Jason]].
* In ''Film/IndependenceDay'' a character makes a passing reference to ''Series/TheXFiles'', conversely, in [[Film/TheXFilesFightTheFuture the first X-Files movie]] we see Mulder urinating in front of an ''Independence Day'' movie poster.

[[/folder]]

[[folder: Literature ]]

* From ''[[Literature/AliceInWonderland Through the Looking-Glass]]'':
-->"What ... is ... this?" he said at last.\\
"This is a child!" Haigha replied eagerly, coming in front of Alice to introduce her, and spreading out both his hands towards her in an Anglo-Saxon attitude. "We only found it to-day. It's as large as life, and twice as natural!"\\
"I always thought they were fabulous monsters!" said the Unicorn. "Is it alive?"\\
"It can talk," said Haigha, solemnly.\\
The Unicorn looked dreamily at Alice, and said "Talk, child."\\
Alice could not help her lips curing up into a smile as she began: "Do you know, I always thought Unicorns were fabulous monsters, too! I never saw one alive before!"\\
"Well, now that we ''have'' seen each other," said the Unicorn, " if you'll believe in me, I'll believe in you. Is that a bargain?"\\
"Yes, if you like," said Alice.
* Creator/RobertAHeinlein's ''Literature/TheNumberOfTheBeast'' introduces the concept of the "World as Myth" which supposes that all fictional universes are equally real and, moreover, are accessible to one another via interdimensional travel. The act of authorship is what creates said universes, which leads to the interesting notion that the characters in any given universe may be controlled, at any given moment, by an Author from another. Or that characters could, in theory, meet their own Author. The novel concludes in a MassivelyMultiplayerCrossover whereby the protagonists host a convention of characters from nearly every ScienceFiction and {{Fantasy}} universe ever.
** The subsequent novels ''Literature/TheCatWhoWalksThroughWalls'' and ''Literature/ToSailBeyondTheSunset'' run with the concept to its logical conclusion, in which the characters wage running pandimensional battles against groups of agents from other realities, all competing to see which can rewrite history to their whims.
* Creator/PhilipKDick ''Literature/TheManInTheHighCastle'' contains a {{Subversion}}. The novel is an AlternateHistory describing a hypothetical timeline in which the Axis won UsefulNotes/{{WWII}} and conquered the United States. [[spoiler:And in the novel's 'verse exists another novel ''The Grasshopper Lies Heavy'', which is itself an AlternateHistory novel describing [[RealLife a hypothetical timeline in which the Allies won WWII]], but which is ''not'' [[RealLife our reality]]. For example, in it, the British Empire is the dominant global power.]]
* Scots author Quintin Jardine has written two long-running series: ''Skinner'', about a high-ranking Edinburgh police detective, and ''Oz Blackstone'', a private detective and part-time actor. In at least one Blackstone novel he is involved in making a film based on the Skinner books, while the Blackstone novels themselves appear in Skinner's world.
* The ''{{Goosebumps}}'' series had a ''recursive'' fiction paradox. For example, a couple of the main books and ''a lot'' of the ChooseYourOwnAdventure books mention the main character having read about something like their situation in a Goosebumps book. In a good deal of the Literature/ChooseYourOwnAdventure books, you need to know about the book being referenced to get a good ending!

[[/folder]]

[[folder: Live Action TV ]]

* Mexican sitcoms ''Series/ElChapulinColorado'' and ''Series/ElChavoDelOcho'' recursively reference each other at different points.
* There was a crossover between PowerRangers and the live-action [[Series/NinjaTurtlesTheNextMutation Teenage Mutant Ninja Turtles]] series. It's particularly amusing when one of the turtles laughs off a mention of the rangers as comic book characters.
* An episode of ''Series/TheTwilightZone'' entitled "A World of His Own" somehow managed to do this to ''itself''. The story deals with a writer named Gregory West who can [[RealityWarper cause fictional characters to appear in real life]] if he dictates descriptions of them into his tape recorder, and cause them to disappear again by burning the tape he described them on. At the end of the episode, [[OnceAnEpisode as is traditional]] Rod Serling appears to give the story's closing narration.
--> '''Rod Serling:''' We hope you enjoyed tonight's romantic story on ''TheTwilightZone''. At the same time, [[ThisIsAWorkOfFiction we want you to realize that it was, of course, purely fictional]]. [[ThisIsReality In real life]], [[WhoWritesThisCrap such ridiculous nonsense could never]]...
--> '''Gregory West:''' ''[suddenly [[BreakingTheFourthWall breaks the fourth wall]] and [[InteractiveNarrator acknowledges Rod Serling]]]'' Rod! You shouldn't!
--> '''Rod Serling:''' [[StunnedSilence ...]]
--> '''Gregory West:''' [[RageAgainstTheAuthor I mean, you shouldn't say such things as "nonsense" and "ridiculous!]] ''[takes out tape labeled "Rod Serling" and throws it into the fire]''
--> '''Rod Serling:''' ''[resigned]'' Well, that's the way it goes... ''[[[MindScrew vanishes]]]''
* In ''MadAboutYou'' there is an episode where Paul visits an old apartment of his. That apartment happens to be Jerry Seinfeld's and he runs into and has a rather poignant conversation with Kramer. But in a later episode of ''{{Seinfeld}}'' George is forced to suffer watching an episode of ''Mad About You'' with his fiancee Susan.
* ''Series/DoctorWho'' is fictional in ''EastEnders'', they have a character who is a fan (Bradley) who even goes to a Doctor Who convention at one point. ''[=EastEnders=]'' is also fictional in ''Doctor Who'' wherein Jackie Tyler is a fan, and ''[=EastEnders=]'' appears ShowWithinAShow style in "Army of Ghosts". The Doctor also references it in "The Satan Pit". There was a crossover between them in 1993 for ''ChildrenInNeed''. In "Dimensions In Time", neither show acknowledges the other's fictionality in it and it isn't considered in continuity for either (one explanation touted by ''Doctor Who'' Spin Off Media is that it was AllJustADream of the Seventh Doctor).
** In fairness, DoctorWho is implied to be fictional ''within itself''. A Seventh Doctor episode had him visit 1963 London, where a TV announcer was cut off half-way through introducing the first episode of a new BBC sci-fi series with the first syllable "Doc-"
* References to characters watching ''{{Passions}}'' started showing up during season four of ''Series/{{Buffy|the Vampire Slayer}}''. Shortly afterward, ''Passions'' characters started watching ''Buffy''.
** Also, characters in Buffy have talked about {{Xena}}, whereas, while they clearly can't have a television show on Xena, there is a play called 'Buffus the Bacchae Slayer'. Of course, as Xena is both told by a [[LiteraryAgentHypothesis literary agent]] and [[NoFourthWall fictional within itself]], it's anyone's guess as to what is actually going on.
* Sort-of real life example - the series ''{{Bones}}'' is inspired by the work of author Kathy Reichs. In the series, the heroine is an author who writes novels about a character named Kathy Reichs.
** The novel character seems very close to the author in personality, though the events of each plot, per Reichs' afterwords, are only based on the broadest strokes of real-life cases. The television character is almost completely different from the novel character. It's really just the names.
** Dr. Temperance Brennan gets a honorable cameo appearance in Fforde's Literature/ThursdayNext series, which ''runs'' on recursive fictionality.
* A tricky one: ''GreenAcres'' coexists with ''Series/PetticoatJunction'', and ''Series/PetticoatJunction'' coexists with ''BeverlyHillbillies'', but Beverly Hillbillies is fictional on Green Acres (and is Eb's favorite show).
** In one episode of "GreenAcres" Eb even watches an episode of "Series/PetticoatJunction"
* ''Series/{{Leverage}}'' and ''{{Psych}}'' are both mentioned as TV shows in each other's universes, but unfortunately, that leads to a WhatCouldHaveBeen, because if ''Psych'' hadn't made ''Leverage'' fictional in their universe, WordOfGod says that ''Leverage'''s [[{{Crossover}} Eliot would've had an uncle named Henry]].
* A difficult case occurs with the 60's series ''Series/{{Batman}}'' and ''Franchise/TheGreenHornet''. An episode of ''The Green Hornet'' establishes that ''Batman'' is a (presumably fictional) television show in his universe, but then the Hornet and Kato appear in an episode of ''Batman'' and help him with a case.
** Also, in the ''Batman'' episode "The Impractical Joker," Bruce Wayne, Dick Grayson, and Alfred are watching a news program about how Batman and Robin were made helpless by a new Joker device earlier in the day. In disgust, Bruce asks to change the channel, noting that ''The Green Hornet'' is about to come on. We don't get to see any of that, as Joker breaks into the TV channel's signal to gloat and taunt Batman over the airwaves.
* In ''Series/TheXFiles'', a character is seen watching an episode of ''WesternAnimation/TheSimpsons''. Fortunately, it's not the episode where David Duchovny and Gillian Anderson appeared as Mulder and Scully. In Comic Book Guy's shop, one can see a poster to the ''X-Files'' movie.
* ''WesternAnimation/EekTheCat'' did an ''X-Files'' parody, and was also shown in an ''X-Files'' episode "Eve" where one of the little murderous clones watched the animation.
* [[Series/{{House}} Dr. House]] watches ''GossipGirl'' and Blair Waldorf watches ''House''. Leighton Meester, the actress who plays Blair, also guest-starred on an episode of ''House'' as a teenager in love with the titular character. In the 2011 movie ''The Oranges'' Hugh Laurie plays a man who falls in love with a friend's daughter... played by Meester.
* In ''Series/{{Community}}'' Abed's favorite TV show is ''CougarTown'' and in one episode he talks about guest starring on it. In one episode of ''CougarTown'' Laurie and Travis watch the first season of ''Series/{{Community}}'' on DVD. This eventually came full circle with Laurie and Travis as bit characters in the season finale of ''Series/{{Community}}'' and Abed as a bit character on the season finale of ''CougarTown''. A later episode of ''Series/{{Community}}'' had Abed, MetaGuy that he is, explaining the MindScrew the whole thing had been for him.
* In ''Series/StargateSG1'', Jack O'Neill makes several references to ''TheSimpsons'', Richard Dean Anderson himself, being a huge fan. In season eight, ''DanCastellaneta'' makes a guest appearence (even agreeing with Jack that Mr Burns is the perfect analogy for the Goa'uld). Just to make it more confusing, Anderson once appeared as himself in an episode of ''The Simpsons'' and, oh yes, they mention his work in ''Stargate SG-1''.

[[/folder]]

[[folder: Tabletop RPG ]]

* While most of the [[AlternateUniverse parallel Earths]] in ''InfiniteWorlds'' are the result of [[AlternateHistory diverging histories]], there are a few where characters "known" to be fictional on Homeline[[note]]the home timeline of Infinity, implied to be our world TwentyMinutesIntoTheFuture[[/note]], such as KingArthur, RobinHood, and SherlockHolmes, exist as real people.

[[/folder]]

[[folder: Video Games ]]

* In {{Atlus}}'s 2011 puzzle game {{Catherine}}, Teddie from ''VideoGame/{{Persona 4}}'' makes an appearance in the form of a figure on a bar table and a mascot on a beer bottle. The main character owns books called "Persona". A scene in ''Anime/Persona4TheAnimation'' shows that Yu Narukami changed his girlfriend's ringtone to the game over theme from Catherine.
** The weird part is that the games ''do'' take place in the same universe - in ''Persona 3 Portable'', Vincent (the main character of ''Catherine'') makes a cameo in a hidden scene.

[[/folder]]

[[folder: Web Comic ]]

* ''TheWayOfTheMetagamer'' and ''The Way Of The Metagamer 2: InNameOnly''. ''In Name Only'' makes the occasional cameo in the original, and it's [[WordOfGod been stated that]] the original exists within the world of ''In Name Only''. Interesting in that ''In Name Only'' does not exist.
* ''{{Homestuck}}'' takes this trope to its [[MindScrew Mind-Screw extreme]] with the events of the main story and the Midnight Crew. In the world of the main characters of ''{{Homestuck}}'' the Midnight Crew are from the latest ''MSPaintAdventures'' series, and the reverse is true for the actual members of the Midnight Crew in ''their'' world. However, WordOfGod along with recent events in the story claim that the the Midnight Crew ''exist within the same canon as {{Homestuck}}!'' In other words, it's not a ShowWithinAShow, it's a [[YourHeadAsplode Show Within]] ''[[YourHeadAsplode Itself!]]''
** To elaborate on the "exist within the same canon", the world of the Midnight Crew is the same world as those of the Trolls, who also exist in (or at least communicate with) the kids in the {{Homestuck}} world, but are from an alternate universe.
*** And, to take things even further, the art style and some of the universe mechanics for Midnight Crew suggest that it ''also'' takes place in the same universe as the previous ''MS Paint Adventures'' comic, ''ProblemSleuth''.
*** Also, Problem Sleuth was apparently in the same universe as [[http://www.mspaintadventures.com/?s=4&p=001555 Jailbreak]] and [[http://www.mspaintadventures.com/?s=4&p=001577 Bard Quest]], and John in Homestuck [[http://www.mspaintadventures.com/?s=6&p=001931 has video games of all three of these.]] [[SerialEscalation There are probably even more tie-ins than that.]]
*** Like the time Jade read a panel of ''Homestuck'', even being pretty true to what John had been doing at that point.
** The paradox is explained by the AuthorAvatar, who is likely sending different comics to different universes.
* A really subtle one with QuestionableContent and Webcomic/{{xkcd}}. Marigold wears an xkcd shirt [[http://questionablecontent.net/view.php?comic=1625 here]], and [[http://xkcd.com/574/ this]] xkcd comic shows one of Hannelore's Twitter posts.

[[/folder]]

[[folder: Western Animation ]]

* In a few episodes of ''InspectorGadget'' he can be seen watching ''HeathcliffAndTheCatillacCats'', likewise ''Inspector Gadget'' has showed up as a TV Show on Heatcliff. Both shows were produced by DiC at around the same time.
** Hector also dressed as Inspector Gadget during a DreamSequence in a HalloweenEpisode.
* A ridiculous example in the first season finale and second season premiere of ''WesternAnimation/SouthPark''; "Cartman's Mom is a Dirty Slut" shows the characters see a promo for the movie "Not Without My Anus" and say they will watch it, and in the second season premiere, which turned out to ''be'' "Not Without My Anus" itself, Terrence and Philip flip channels and watch part of the former ''South Park'' episode (where you can at least hear Cartman's name).
* An episode of ''WesternAnimation/TheSimpsons'' has a guest appearance by Richard Dean Anderson playing himself, where his work in ''Series/StargateSG1'' is referenced. However ''in'' Stargate, Rick's character, Jack O'Neill has openly talked about his love of The Simpsons many times, including comparing Mr Burns to the Goa'uld. The icing on the cake is when Dan Castallaneta make a guest appearance on Stargate...and agrees with Jack's Burns = Goa'uld theory!
* ''TheSimpsons'' has MattGroening introduced as "the creator of Futurama". Another one has Bart Simpson hallucinating, his classmates appearing as fictional TV characters, one of which is Bender. Finally, a ''WesternAnimation/{{Futurama}}'' episode has a pile of Bart Simpson dolls appear as one of the many things in a gigantic (indeed, celestial) ball of garbage.
** Also, in the ''Simpsons'' episode ''Mayored to the Mob'', Üter wears a ''Futurama'' shirt ([[ProductionForeshadowing this episode aired about a month before Futurama's first episode]].)
** Also, thanks in part to certain [[ManateeGag trope]]-[[TropeNamer naming]] episodes of ''WesternAnimation/SouthPark'', and innumerable references to each other, ''WesternAnimation/SouthPark'', ''FamilyGuy'', and ''TheSimpsons'' are all fictional within each other's Universes.
** In one episode of the first season of ''LoisAndClark'', LexLuthor made a mention about watching Simpsons reruns. In one ''Simpsons'' episode, Comic Book Guy saw some problem and said it was a job for, [[BaitAndSwitchComment some heroes he mentioned]]. Then somebody asked about {{Superman}}.
* For additional mindwarping, ''TheSimpsons'' is a cartoon in ''WesternAnimation/TheCritic'' - and then Jay Sherman visits the Simpsons family. Gah!
* This trope even occurs within a single show: ''WesternAnimation/SouthPark'' and ''[[ShowWithinAShow Terrance and Phillip]]'' have watched each other's television shows. This gets a bit muddled as Terrance and Phillip are "real" actors in the South Park universe with a television show the South Park kids watch, but the characters (one assumes) Terrance and Phillip play have watched ''South Park''. Do what now?
* In ''WesternAnimation/DannyPhantom'', Danny can be see playing a ''Crash Nebula'' arcade game. In the ''Crash Nebula'' PoorlyDisguisedPilot episode of ''WesternAnimation/TheFairlyOddParents'', Crash has a ''Danny Phantom'' comic book.
* An episode of ''WesternAnimation/AmericanDad'' ended with Peter and Cleveland appearing, but another one had Steve and Roger watch a WesternAnimation/FamilyGuy DVD.

[[/folder]]
----