It then sank in deep water, apparently suffering a radiation problem. Unconfirmed reports indicated some of the crew were rescued.
But according to repeated statements by both Soviet and American governments, nothing of what you are about to see... ever happened."
One possible definition of what differs between Science Fiction and Fantasy is the possibility of events taking place in "our" world. A Masquerade is required. Thus, when Science Fiction shows us The Future, we are meant to believe that it is our future; which means that their past is our present, and therefore has to look like it.
According to this school of thought, if you want to do Science Fiction in the present day without pushing the Reset Button, you must maintain "plausible deniability": it must be possible for the audience to believe that the events depicted "really did" happen, and they just didn't hear about it.
So, nothing can happen in the present which would make the six o'clock news. If you want aliens to show up, they can't land on the White House lawn and ask to talk to the press corps; they have to do it in secret. If you want to have super advanced Applied Phlebotinum, it has to be a top government (or industrial) secret, and can't be something you'd pick up at the local department store. If you want to have an Extraordinarily Empowered Girl, she needs to be sworn to keep her identity a secret.
This usually leads to a Government Conspiracy which keeps the average joe from finding out what's "Really Going On". You may alternatively have some magical or technological reason that these events are Invisible to Normals.
If your show is set in The Future, you get a lot more leeway, but you have to be careful when you talk about history. This tends to go horribly, horribly wrong when a show runs for a very long time and is rerun years later.
This is far from a universal trope, and, indeed, the gymnastics writers have to go through to have a long-running series maintain plausible deniability have become increasingly transparent. More and more writers have abandoned this notion, explicitly setting their series in an Alternate Universe. All the same, the urge is sufficiently strong that you may see an isolated lapse into plausible deniability in a show which does not normally bother.
Compare Pseudocanonical Fic, which has the same relationship to the canon story as Secret History does to Real Life, and Written by the Winners and Internal Retcon, where the people in power in-story have their own "official" version of history. Contrast Like Reality Unless Noted when the world is similar but some events happened differently (e.g. using Our Presidents Are Different to avoid having to depict a real head of state), Alternate History when a work is set in a world like our own but with significant changes, Never Was This Universe when a work is apparently set in Real Life but later revealed to take place in a very different history.
- At first Gainax's anime Nadia: The Secret of Blue Water seemed to use this trope. It took place in 1889 and features remnants of Atlantean civilization fighting a covert war right under the world's nose, without seeming to affect history in any way. However, apparently at the end of the series they just said "screw it" and have a giant flying saucer blow up the Eiffel Tower, a 1/4 of Paris, and project giant holograms all over the world.
- In the second chapter of Busou Renkin, Kazuki and Tokiko look up "alchemy" in an encyclopedia, and find that its main goals were the Philosopher's Stone and transmutation of base metals into gold. Tokiko explains that this is "public knowledge": the homunculi and busou renkins were kept secret. (The Masquerade falls apart to mostly comical effect later in the series.)
- Invoked in The Adventures of Buckaroo Banzai Across the 8th Dimension when it is discovered all of Yoyodyne's employees have their date of birth listed as the day after broadcast Orson Welles' The War of the Worlds.
- The Hunt for Red October opens with a text crawl stating that the events of the film (an Akula/Typhoon-class ballistic missile submarine's Command Roster defecting to the United States with their boat, causing a manhunt by the USSR's entire Atlantic fleet) were covered up by the United States and Soviet Union, but they and the film itself both imply that they partly led to Mikhail Gorbachev becoming Soviet Premier.
- Downplayed in National Treasure: The Gates family lore about America's Founding Fathers hiding away the Templar Treasure isn't secret, so much as discredited by mainstream historians and therefore not taught to the public.
- The Transformers Film Series claims on a number of occasions that various events of the backstory involving human-Cybertronian encounters are not known to the public because they either occurred in prehistory, or the world's governments (mainly the United States) kept them strictly under wraps.
- Animorphs: In Megamorphs #2: In the Time of the Dinosaurs, the cast side with an alien species (the Mercora) at war with another (the Nesk) during the end of the Cretaceous period. The Nesk, being sore losers, leave the planet but redirect a passing comet so that it will crash on the planet, causing the K-T extinction event. The Mercora plan to use a nuke the Animorphs acquired to detonate the comet before it lands, but Tobias has Ax make the nuke into a dud. He later justifies his actions by saying that the Mercora cannot be allowed to survive, as the presence of a flourishing sentient species would prevent humanity from evolving. The fact that they only had a single settlement directly under the impact site explains why no Mercora (who look vaguely crab-like) fossils have ever been found (though they're apparently responsible for broccoli's existence on Earth: it was a staple Mercora crop that survived the impact).
- Artemis Fowl: Fairies have managed to remain hidden even from modern tech thanks to performing mindwipes on humans who see them. They actually have two types: a blanket mindwipe which is done in the field with little equipment necessary, and a more precise version where they remove select memories (in both cases, the human's mind connects the dots and finds its own excuses for what it was doing at the time, but the real memories can resurface with proper stimulation). Artemis himself doesn't know how to prevent it, but he did figure out a way to restore their memories by leaving prerecorded messages to himself and to Butler (he even figured out a way to prevent the fairies from making him reveal his failsafes, by leaving one with Mulch and leaving it out of the ones he "confessed" to).
- Tim Powers novels:
- How Doyle gets around You Already Changed the Past in The Anubis Gates. Since he turns out to be the only source for Ashbless' life, he doesn't need to do what the history books say; he just has to remember what the history books say so he can recite them as Blatant Lies later.
- Declare answers the question of why most of its events surrounding very real historical people and circumstances are not known to public by saying that the British, American, and Soviet secret services covered all of it up after the fact.
- Subverted in Charles Stross's multiple-parallel-universe The Merchant Princes Series. For the first few books, everything could plausibly be going on under our noses, with strange events being passed off as hoaxes or terrorist attacks. He blows the lid off the masquerade at the end of book five when a dissident faction nukes Washington D.C. It's revealed in passing that the main universe isn't ours, but a slightly different one—in which, for example, Saddam Hussein is killed in a coup just before the U.S. invasion.
- Throughout The Saga of Darren Shan, author Darren Shan claimed in interviews that the series was a nonfictional autobiography, despite its fantastic elements (such as the protagonist getting turned into a half-vampire). At the end of the series, this is explained by the books' Darren changing history so that the events of the series never happened, and handing his memoirs to his alternate self with instructions to publish them.
- Downplayed with Star Trek: The Eugenics Wars. Greg Cox made a heroic attempt to clear up a notorious Continuity Snarl and explain how the Eugenics Wars (an important element of Star Trek's established history of the future) could have taken place in the real 1990s without anyone noticing. Mostly they took place in the background of the post-Cold War brushfire wars (it still had Khan ruling part of India openly, which obviously did not happen, but the rest took place behind the scenes).
- The Lord of the Rings and all of Tolkien's other works, are supposedly this. Tolkien, referring to the Valar, said they were beings "whom in later ages Men called Gods": the men he was referring to were those from the ancient civilizations that we know of from history. In particular perhaps, the Norse. He also liked to playfully slip actual words into his elvish languages. Like how conveniently Exilic Quenya changed the letter thule, to sule: so that the name Thauron, became Sauron. Which is Greek for lizard. He also had Common Telerin börn, become "beorn" in the Nandorin dialect: which evidently entered the Mannish tongues as well. Beorn is of course German for bear, and we meet this word as the name of a werebear. This wasn't confined to elvish either. Tolkien inserted the word "Avalon" into Adunaic, the language of the men of Numenor: though the root of the word was borrowed from Quenya elvish. If you look at the complete map of Middle Earth (found in the Silmarillion), the landmasses are also seemingly very familiar, although evidently plate tectonics have been at work. He even provides an explanation for why the world is now round. Of course, Tolkien was fully aware that all of this was mythology and explicitly stated that it was. He never intended for a reader to take this Secret History he'd made up very seriously.
- The Percy Jackson and the Olympians series begins with Percy proclaiming everything in the book to be true. He's tells the reader that he's envious of the reader for being able to think it's fiction. He then warns them to stop reading immediately if they believe they might be a demigod, lest monsters begin showing up on their doorstep. In-story, all of the mystical mishaps are covered up by the Mist, a device taken from The Iliad that obscures what happens so that mortals can rationalize it. For instance, if Percy is holding a sword, a mortal onlooker would see it as a baseball bat. This is also why the gods' involvement in major events like World War II has never been recorded by any mortal historian.
Percy: If you're a normal kid, reading this because you think it's fiction, great. Read on. I envy you for being able to believe that none of this ever happened. But if you recognize yourself in these pages - if you feel something stirring inside - stop reading immediately. You might be one of us. And once you know that, it's only a matter of time before they sense it too, and they'll come for you.
- At the end of Battlestar Galactica (2003), the surviving Colonials abandon all technology, all of it, ostensibly because Ludd Was Right, but really it's because Ron Moore didn't want viewers wondering why there's no evidence of space-flight technology from hundreds of thousands of years ago, as if viewers of science-fiction wouldn't grasp the concept of fiction.
- The Black Adder shows an Alternate History of the Wars of the Roses where the the Yorkists actually won the Battle of Bosworth Field, but King Richard III York was mistakenly killed by his grand-nephew Prince Edmund "the Black Adder" shortly afterwards and Richard IV, one of the historical Princes in the Tower, was crowned his successor. The Opening Narration of the first episode states that King Henry VII Tudor, who historically won at Bosworth Field, rewrote the history books to ruin Richard III's reputation and erase Richard IV's entire reign after gaining the throne.
- Borgia: The Roman sculpture Laocoön and His Sons is unearthed sooner than it was in real life. Rodrigo Borgia dislikes the implications of it towards his family so much that he orders it re-buried, explaining its later rediscovery.
- Star Trek: Voyager: "Distant Origin" attempts to explain away the lack of archaeological evidence of the Voth civilization on Earth by saying they evolved on an eighth continent which was destroyed after they left. (Cue the Fridge Logic of how they managed to invent spacecraft before boats, never mind the Artistic License Geology.)
- War of the Worlds takes the unusual stand that most of humanity simply doesn't remember the massive and very public invasion of the 1950s. There's no major government coverup, and most humans could probably find out about it if they really tried, but most people just find alien invasions too far outside their normal sensibilities to think about it very much.
- The RPG Colonial Gothic involves the players waging the secret Weird Historical War battles of The American Revolution.
- Conversed in Conspiracy X, whose guidebooks encourage Chroniclers (dungeon masters) to use real life history as a basis for their storylines.
- Paranoia uses this as part of its setting: nobody is completely sure what history actually consists of because it's been edited so much.
- Pathfinder: The Reign of Winter campaign path makes use of this trope throughout certain parts of the campaign but most notably in its fifth book, Rasputin Must Die! Unbeknownst to recorded history, Rasputin is the estranged son of the witch Baba Yaga (yes, that Baba Yaga). His death in 1916 was faked, and the reason for his persistence during that assassination is that his soul is stitched to his body. The party is tasked with stopping him and finding the trapped Baba Yaga. Furthermore, a good part of the adventure takes place in a fortress built with magical devices based on the notes of Nikola Tesla. His death in this adventure allows events outside of the Secret History to be resolved as normal.
- Cultist Simulator has five different and mutually exclusive histories, all true. You can visit locations from all of them.
- In the Assassin's Creed series, the Templars, an Ancient Conspiracy, have effectively controlled all of history. Although almost every important figure in history was a Templar (or a member of the rival Assassins), the Templar ensure that the history books never reveal any evidence of the ongoing Secret War.
- According to Empire Earth 2's American campaign, the Soviet Union truly collapsed after the US stole the stealth bomber the Soviets had developed, both sides managing to hush up the whole naval war in Alaska.
- Metal Gear Solid 3: Snake Eater: Officially, the Soviet Union stopped building a nuclear missile base in Cuba, and removed the missiles already there, in exchange for NATO removing nuclear missiles from Turkey. The Turkey missiles were obsolete and going to be decommissioned anyway. According to the game, this covered up the Soviets' desire for having a scientist who defected to the West returned to them.
- Nasuverse: In the Fate series, it's mentioned in the lore that parts of both mythology and history as we know it might've been wrong or misleading and that the series shows (some of) the truths of said myth and history.
- In Fate/EXTRA, Sir Francis Drake (the famous 16th century privateer) is apparently a woman. Her bio notes that the reason history recorded her as male is because she's so much of The Lad-ette (acting rough, talking like a sailor and heavily drinks) that her crew refer to her as a man, otherwise they don't feel manly themselves.
- Creepypasta "TEH DAY OF ALL TEH BLOD" ends by claiming the main character of the story is you the reader, and that you forgot it all happened.
- SCP Foundation: The often horrifying nature of SCPs (both their effects on people and the circumstances of their retrieval) is usually treated with Mind Wipes by the Foundation. However, one story posits that if amnesics sound like a convenient plot device to allow the Foundation to continue its work unhindered, it's because they are: the so-called memory wipes actually consist of a doctor Mind Raping people into fearing to tell about what they saw. Due to the Loose Canon nature of the SCP 'verse, whether this is true or not is up to the reader: given the level of tech exhibited in some cases, the Foundation could likely selectively remove memories.
- The Fairly OddParents! explains that, after a child outgrows or otherwise loses their fairy god parents, their memory of ever having them, along with anything they wished for, would be erased out of existence. This, along with witnesses having their memories wiped and children being required to keep their fairies a secret, means that the series could take place in our universe, with everyone just forgetting that fairies exist after every encounter with them.