This is lampshaded in Macross 7, in which Mylene and Basara appear in a remake of the movie, and Max and Miriya (who were there for the original events) comment on some of the exaggerations and distortions therein.
Macross Frontier had an episode which adapted the events of Macross Zero into a movie, which was mainly an excuse to lavishly reanimate some of the more distinctive bits of Macross Zero, as well as allude to similarities between the characters of both series. It was based on Bird Human, the biography of one of the main characters of Macross Zero.
Sound Stages reveal that Magical Girl Lyrical NanohaThe Movie First is an actual film being produced in the Nanohaverse about the childhood of Nanoha and Fate, with those two serving as technical advisers to make sure that the facts are reasonably accurate and that the battles are as realistic as possible.
Baccano! the first light novel, The Rolling Bootlegs, begins with a Japanese tourist being told the events of the book by a mysterious young man, who is later revealed to be Firo Prochainezo.
The manga version of Chrono Crusade hints at this—a few chapters at the end "quote" from Azmaria's memoirs, hinting that the manga may be a fictionalized version of her book.
Digimon Tamers is possibly unique in the Digimon canon as it is set in a world where the Digimon franchise exists. Takato actually has Digimon trading cards and has seen season one and two! This becomes even more interesting when the kids realize that the people who made the Digimon used their work to start the franchise.
YuYu Hakusho, in the anime at least, is revealed at the end of the penultimate episode to be a compilation of footage taken by Spirit World as they monitored Yusuke's adventures.
In Marvel Universe continuity, there is a "Marvel Comics" company that re-tells the exploits of various heroes as comic books. They're quasi-journalists, and their work is thus used as historical research in legal comedy series She-Hulk. In continuity, the Fantastic Four regularly popped by the Marvel offices to lambast the staff who were supposed to be telling their stories over plot elements that they didn't like. Similarly, Steve Rogers not only lectured writers and editors for making him too violent, but also at one point penciled his own comic.
Similarly, Astro City has established the presence of several comic-book publishers; some are direct analogs in the real world (DC, Wildstorm), but others are strictly fictional (Bulldog, Rampart). It is further stated that some publishers chronicle the real-life exploits of the Astro City superheroes, though laws require these comics to adhere to published facts and secure licensing rights. The story "Where the Action Is" details one such publisher who repeatedly gets into trouble for exaggerating and/or misrepresenting the behavior of the real superheroes and villains... and cosmic entities.
Most issues of What If? are told by the Watcher, who watches not just the usual Marvel Universe, but the whole multiverse.
Also in Marvel Comics, The Sentry originally was based on a supposedly lost series of comics from the golden age, featuring a more traditional invulnerable-and-superstrong character. The new series dealt with why nobody remembers this classic character existing before in a very meta-way. They come up with a save-the-world explanation in the fictional universe for his fictional nature... then it gets complicated.
Most citizens of Marvel Earth believe the Frankenstein Monster to be a fictional character, and don't realize Shelley's novel was based on real events. Ditto for almost every character from Norse and Greek mythology.
DC Comics exist in the DCU. They use superheroes' status as public figures to publish "true crime" stories about their adventures.
Superman gives all the profits of his comics to charity.
The Teen Titans have one. Impulse gave the company their real names because he didn't know that wasn't how everyone did it. He called Superman "Dirk" for months.
Batman does appear in the DCU's DC Comics; a late 1960s Batman comic's plot revolves around the (DCU) Batman comic and its writer.
Barry Allen's Flash knew of Jay Garrick's Flash through comics before he learned the fella existed in another universe/sealed-off reality.
Captain Carrot and His Amazing Zoo Crew! uses this aspect in its Earth-C setting: Cap himself works for his world's DC Comics, which publishes adventures of the (fictional to them) "Just'a Lotta Animals"... eventually discovering that the characters were real, existing on the parallel world of "Earth-C-Minus." The story even involves the heroes consulting Earth-C's Gardner Fox — an actual fox, natch — for advice on this phenomenon.
Mark Millar wrote a story for a Flash 80-Page Giant called "Your Life Is My Business" in which his DCU counterpart chatted with Wally West about possible story ideas. This briefly alluded to the fake secret identities used in comics before so many heroes went public, and had various practical reasons why some stories couldn't be used (such as one featuring Zatanna's pre-teen descendent from the 30th century; he can't appear in a comic without his parents' permission, and they're still in the future).
IPC's comics used this frequently.
2000 AD had (and still has) The Mighty Tharg, an alien on a quest to strengthen humanity by exposure to 'Thrill-power', which he does by publishing a comic.
Goody Two-Shoes was a supervillain. Kinda. He appeared only once, had nuclear-powered shoes, and kicked the hell out of the Thing by himself. Then the Thing managed to defeat his terrible foe. Then, the "real" Thing read the comic-book and went to the editorial absolutely pissed. We realize then that Goody Two-Shoes was defeated with a flick from the Thing, and they made up the whole fight to make the story interesting. Then the Thing does them something... uh... interesting.
Alan Moore claims to have met John Constantine of Swamp Thing and Hellblazer fame in real life, more than once... Maybe he just ran into Sting and he happened to be in a trenchcoat and a playful mood.
We must consider two very distinct possibilities. Either Alan Moore is out of his friggin mind, or that he believes so much in certain things, that they become real, and his sanity forces him to forget lest he obliterate himself. (The latter does in fact broadly fit his belief system.)
Early drafts of the script of Star Wars describe it as having come from records called the "Journal Of The Whills." Given how much George Lucas has muddied the waters, though, it's hard to know what he intended in 1977.
George Lucas later said that the entire Star Wars saga is being told by R2-D2 (which probably is why he's always saving the day).
The Spanish film Voyage to Nowhere (1986) features an old Carlos GalvŠn telling the story of his life to a biographer. In those scenes, GalvŠn himself admits that his recalling of events cannot be 100% correct and, at some points, he had intentionally taken another people's sentences as if they had been his. Simply because it looks cooler that way, you know.
Copacabana: a performer-turned-agent (played by Groucho Marx) gets his girlfriend (played by Carmen Miranda) two separate, simultaneous gigs at the Copacabana - one as herself in the main room, and as "Madame Fifi" in the nightclub. At the end of the film the owner of the Copacabana decides to make a film about it, starring them, and we see the Big Production Number in the film.
Scream 2 has the movie Stab, which is the in-universe movie made about the events of Scream.
Mentioned in Hook, the film "sequel" to Peter Pan. Wendy Darling and Peter Pan had adventures that Wendy later told to J.M. Barrie who, we presume, made a few changes, which accounts for the inconsistencies between the book and film. For example, Captain Hook is eaten by the crocodile in the book whereas in the film, Hook escaped the crocodile and killed it instead.
The Heralds of Valdemar books by Mercedes Lackey may possibly be an example — frequent reference is made to Herald-Archivist Myste (Lackey's Author Avatar; her nickname is "Misty") who is occasionally said to be collecting accounts of the adventures recounted in the books.
The comedy/crime novel Jimmy the Kid features some bumbling crooks who plan out a kidnapping based on a novel, Child Heist by Richard Stark. While Child Heist doesn't actually exist, Richard Stark is another pseudonym of Jimmy the Kid's author, Donald E. Westlake. This makes the latter novel an extended running gag on this trope, as Westlake pretends that Child Heist exists within Jimmy's world.
Much of the plot of Bram Stoker's Dracula is about the construction of the book itself and how Mina Harker's compilation of the characters' journals, interview transcripts, and the like helps the characters deduce Dracula's identity and nature and ultimately defeat him. To some extent, the book is practically an advertisement for that wondrous new invention, the typewriter.
In The Dresden Files, it's heavily alluded to that Dracula was pretty much commissioned from Bram Stoker, so people would have a defence against the Black Court. In Grave Peril, Harry mentions that the Black Court is almost nonexistent, thanks to that book. And, in one of the recent "extra" stories, it's pointed out that the Necronomicon was actually a Grimoire of great power — until the White Council found it and published it all over the place, and by making it available to every minor mage and wannabe in existence, effectively nullified the power by spreading the effect over the entire world.
In an interview with the author, a fan asked whether H.P Lovecraft was onto something in the same way. The answer - yes. Oh, Crap.
It's explained in a minor book. There are Outsider style grimoires that do NOT follow the 'spreading' rule. They get MORE powerful the more people believe in them. One of these is ALMOST discovered by Harry. Thomas is responsible for making sure no one learns about this kinda stuff.
Both The Hobbit and The Lord of the Rings are revealed at the end to share the same title as a book written by the lead character at the end of each (There and Back Again: A Hobbit's Holiday and The Downfall of the Lord of the Rings and the Return of the King, respectively). Bilbo's uncompleted "Translations from the Elvish" is claimed to be the (then-unfinished) Silmarillion.
The hypothesis was also used to excuse a Retcon of The Hobbit. In the original edition of the book, Gollum is quite willing to hand over the Ring itself as a prize for winning the riddle contest — utterly out of character given the plot of The Lord of the Rings, so later editions change that scene. The preface of The Lord of the Rings justifies the correction by noting that Bilbo himself wrote the original The Hobbit as memoirs and, already slightly corrupted by the Ring, lied about how he got it when he put the tale to paper; Gandalf eventually talked him into revealing the truth.
The Red Book itself is said to have a companion volume of "Translations from the Elvish", which presumably contains the source material of The Silmarillion. Many of those texts are attributed to specific Elvish scribes.
The AkallabÍth (one of the stories in The Silmarillion) is attributed to Elendil, a Man, and supposedly came from a copy of the Red Book as preserved in Gondor, rather than as one of Bilbo's translations.
Inferno, a modern retelling of the Inferno from Dante's The Divine Comedy, mentions that Dante's description and maps of Hell are accurate, and have been used by other visitors. Phlegyas, boatman across the swamp in the fifth circle, is particular annoyed that Dante gave away the phrase that means he has to transport the speaker to the City of Dis.
Bertie Wooster, narrator of the Jeeves and Wooster series, makes several references to himself as the author.
In the Knight and Rogue Series Makejoye writes a play about a handsome but poor lad and a dashing bridand who was forced into a life of crime thanks to corruption in politics competing for the same lovely high class lady who'd run away from her uncle. Just in case it's not obvious that the play is really about the actor Rudy, the unredeemed Michael, and the runaway Rosamund, he has all of them playing the appropriate roles.
House of Leaves is about a film, but it is also about a man named ZampanÚ writing a critical essay on the film, and it is also about a guy named Johnny Truant reading the critical essay about the film after finding ZampanÚ's body. Some of the dramatic tension in the story comes from the fact that, while the film itself is non-fiction, and ZampanÚ's essay is nonfiction and references multiple other reviews of the film, Johnny is unable to find any evidence that the film ever existed.
In The Sign Of Four, Sherlock Holmes comments that he's read the account Watson titled A Study In Scarlet, and wasn't impressed.
The pronunciation guide at the back of the Deverry books by Katherine Kerr includes references to an ongoing fued between the author and a professor of Elvish about the simplifications she uses. There are also a few references in the text itself suggesting that the books were written by a Deverrian, some centuries after the period in which they're set. The final book names this author as Cadda Cerrmor, which in Deverrian would be pronounced "Katha Kerr-mor".
As of First Amongst Sequels, the first three Thursday Next novels sort of exist in the Nextiverse, although they're very different to the real world versions. Until Thursday alters them to match our versions, just as she did to Jane Eyre in the first book. Thursday's unwanted fame has therefore increased, and worse yet, people expect her to act like the fictionalised version.
Live Action TV
Some people believe that the show Wormhole X-Treme! is actually a way to create plausible deniability for a real Air Force project called "Stargate". As the Air Force will tell you, this is a complete lie.
Of course, not only is that what they'd say if it was a complete lie, its also exactly what they'd say if it was complete truth. Not that anybody ever saw the show. It was on cable, after all.
The series finale of Star Trek: Enterprise was controversially framed as a non-interactive holodeck recording being viewed by Next Generation characters Troi and Riker, who occasionally paused the episode to discuss things. Early rumors suggested that the entire series would be revealed to be a holodeck recording (or worse, a simulation), but there's no evidence of this in the aired episode. A lot of fans still found it to be an inadequate send-off, although others who viewed it as a send-off to the entire franchise (since, for the first time in 20 years, there were no further Star Trek shows or movies in the pipeline, and, as of now, this is the last Star Trek show or movie set in the original continuity) were a bit more accepting of the shifted focus.
Of course, this allowed some of the fridge logic to ret-con the episode as a piece of doctored history.
As was done by the Enterprise novel The Good That Men Do, which proposes that what Riker watched was Trip's cover story, and that he'd really gone undercover in Romulan space. The novel verse takes this explanation and runs with it.
Supernatural: In Monster at the End of the Book, Chuck is seeing visions and writing them down, believing them to be fiction. However, it turns out later that they are a divine prophecy telling the actions of the main characters, and that his writings will eventually become holy texts.
There's a popular fan theory that the Dr. Who and the Daleks movies (with Peter Cushing as human Mad Scientist "Dr. Who"), loose adaptations of Doctor Who storylines "The Daleks" and "The Dalek Invasion of Earth", are in-universe movies made with some involvement from Ian and Barbara, the companions in both of those stories. This theory almost got Ascended Fanon treatment in "Day of the Doctor" - Kate Stewart was supposed to have the movie posters on her wall - but they couldn't afford the rights to the posters.
It should be noted that giving samples of "genuine in-world text" is one of best methods to demonstrate a setting's flavour and encourage non-OOC style.
The Dresden FilesRPG is presented as a draft version of an in-universe RPG based on the setting, with notes and queries by assorted characters, and text marked for deletion with angry notes from Harry Dresden about not giving away White Council secrets.
Many of the recent BattleTech universe books are seen as this, being collections of news, dissertations and rumors. In Brush Wars, the text even argues with itself at some points, and one page-long portion is written in a partial substitution cypher to simulate a botched transmission of a message.
There are a half dozen hints (one of which had to be decoded by the reader in order to be understood) across 4 different books released in that last 5 years that hint at something that makes a lot of sense, that Clan Wolverine joined Comstar after fleeing the Homeworlds, and during the next 300 years quietly gained significant influence over the organization, and after the Word of Blake Schism have nearly complete control over Word of Blake. The point of all of this was to try to unite the Inner Sphere under their leadership against the eventual clan invasion. The rumors surrounding what happened to them are among the oldest in canon, with the very first ground work laid years before the clan invasion event, which started in 1988. More and more rumors were added over the following 2 decades, weaving a murky and complicated tapestry of half-truths, rumors, and questionable intelligence reports. Even among diehard fans, the above spoiler is open to question, as the actual events that make the connection happened centuries ago in canon. Deep and complicated mysteries are quite at home in a universe with 800 years of history, including a 300 year period with maybe 2 decades of peace, in fact things being lost into the pages of history and coming back, (possibly with a vengeance) are a recurring theme in BattleTech.
Dungeons & Dragons is implied to be this in the d20 Modern Urban Arcana setting (at least in Broad Strokes fashion). The adventure in the sourcebook mentions that the first mage you encounter runs a bookshop with a tabletop RPG section, drinks coffee from a "World's #1 wizard" mug, and D&D is the game that started it all. Plus, you met Estevan from the "Planar Trade Consortium", both being important actors in the Planescape D&D setting, who explicitly makes trips between the shadow and the modern world.
One of the Cursed Artifacts in Ghostbusters: The Video Game is a DVD of the movie Ghostbusters. In the item's backstory, it was brought into the past by the Cult of Gozer in an attempt to see what the future would bring.
One episode of The Legend of Tarzan focused on an American writer named Ed who hears about Tarzan's exploits and interviews people about them, eventually meeting Tarzan and Jane themselves. Of course, the episode ends with the finished book and the name Edgar Rice Burroughs on the cover.
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