When the heroes of a story are told a myth, legend, or fairy tale, you can almost guarantee that the story is true (although not necessarily literally—sometimes the truth is filtered through generations of retelling and/or a primitive culture's viewpoint) and the heroes will have to deal with it at some point. This is used so often, in fact, that it's actually more notable when the heroes are told a story and it doesn't turn out to be some flavor of true — except for those cases where it comments thematically on the heroes' journey and Character Development.
This is largely a result of The Law of Conservation of Detail, which demands that taking time out from the main story to tell some other story must only be done when that side story is important to the main plot.note The purpose in labeling something important as a myth rather than just explaining it outright is to build excitement, so that when the legend is later shown to be true, it brings a sense of wonder or discovery. It can also serve to foreshadow future events, while giving the author an excuse for giving only partial or deceptive information.
Compare to Prophecies Are Always Right, where it's a prediction that's virtually guaranteed to be right rather than a story from the past. These two tropes often live side by side, with the ancient legend packaged with an included prophecy.
Contrast Shrouded in Myth, where the heroes initially believe a legend that turns out to have been extremely exaggerated (if not outright false), and Legend Fades to Myth, where the reader is shown an inaccurate, mythical version of events they saw first-hand in a previous work, generally for humor or Dramatic Irony. Related to All Myths Are True.
Note that this trope is about the characters within a story being told a myth, which turns out to be based on actual events within the story's universe. This is not about an author using real-world myths in a story (though the myth the heroes are being told may well be borrowed from a real-world source). Also compare Infallible Babble, the video game equivalent for rumors and legends imparted through NPCs.
- Saiunkoku Monogatari begins with Shuurei telling her students the story of their country's founding, ending it by saying that according to legend, the eight immortal sages who helped the first emperor found Saiunkoku are still alive in secret among the people. This is absolutely true, and Shuurei goes on to become personally acquainted with several of them. A little later in the first arc, Shuurei begins to tell Ryuuki the story of the Rose Princess and how she married a mortal man. This story is not only true, it's the story of her parents' marriage.
- In Fullmetal Alchemist, the ancient Xingese legend of the Western Sage is about Ed and Al's father, while the Amestrian legend of the Eastern Sage is about "Father," the Big Bad of the series.
- In Dragon Ball Z, the legend of the Super Saiyan, believed to be the most powerful being in the universe comes up, originally in a passing reference in the Vegeta Saga, then suggested in the Namek Saga during the Namekian Great Elder's encounter with Krillin, then brought into the forefront when Goku arrives on Namek and easily mops the floor with the Ginyu Force. Notable in that, the Big Bad Frieza knows about this legend as well, claiming not to believe in it, yet is discovered to have committed genocide against the Saiyans largely because of it. Ultimately, his own actions end up creating one, in the form of Goku.
- In the Jaya and Skypeia arcs of One Piece, the Straw Hat Pirates investigate the legend of "Sky Island" and its City of Gold, which all turns out to be true, even down to most of the details.
- Mazinger Z and Great Mazinger: Dr. Hell joined an archaelogical expedition to the Greek island of Bardos, thinking that maybe several ancient legends telling of the island being defended by an army of mechanical giants were true. Unfortunately for everybody else, he was right. Classical Mythology plays an increasingly important role in each retelling of the series, until the point of Greek gods start showing up and Great Mazinger Big Bad is revealed being Hades in Shin Mazinger.
- A Certain Scientific Railgun has as a running gag the characters mentioning urban legends that all end up being true. It is frequently Lampshaded and otherwise commented upon.
- The second episode of Baccano! gives us the Urban Legend of the Rail Tracer: a monster that slowly snatches up and devours the passengers of the train on which its tale is told on. Then a 3-way war breaks out over train-hijacking rights and...something decides to start picking off instigators and leaving their twisted and mutilated corpses. Turns out that the Rail Tracer is the entirely human and supposedly dead train conductor that first told the story, and doesn't particularly like people messing up his train. Did we mention that he's also a not-entirely-sane assassin that likes a good Roaring Rampage of Revenge?
- In most cases, the Matoran consider most of the Turaga's stories as mere fairy tales. But most of them wind up becoming painfully true. From giant Manas to the hellish Karzahni.
- In the backstory of the Matoran, which claimed that the Great Spirit brought the Matoran out of darkness to the island of Mata Nui. We later find out that it was actually the Turaga who rescued them (as Toa Metru) from their ruined city; they just credited the Spirit with giving them the strength and abilities to do so.
- In Castle in the Sky, Pazu believes the city of Laputa exists from the start when other say it's just a myth. He's not wrong, otherwise the movie would be a lot less interesting.
- In Treasure Planet, Jim's mother assures him in the opening scene that the planet's just a legend.
- In Tinker Bell and the Lost Treasure, the song "Fairy Tale Theater" just happens to be a prophecy of her journey later in the movie that was being performed the one night that she went to the theater.
- My Little Pony: Equestria Girls Legend of Everfree: The eponymous legend of Gaea Everfree starts out as a campfire tale by Timber Spruce. Not surprisingly, it is bound to become important later, although it's a subversion: the legend doesn't happen so much to be true than to be a cover story for the supernatural shenanigans already happening, as a result of Gloriosa Daisy meddling with a magic she doesn't understand.
- In An American Tail, Papa Mousekewitz entertains Feivel and his sisters with the story of the Giant Mouse of Minsk, a giant mouse who scared away the cats. Later, when the mice of New York are planning to do something about the cats oppressing them, it's Feivel who suggests building their own Mouse of Minsk to attack them.
- In The Secret of Roan Inish the grandfather tells the legend of the selkie, which is important to the climax of the film.
- Indiana Jones: The Jewish story of the The Ark of the Covenant and the medieval Christian tale Holy Grail are both proven to be unambiguously true. But so are some elements of Hinduism and the legend of the Crystal Skulls. Not to mention (much as some people would like to pretend it didn't happen) stories of extraterrestrial visitation, and theories about Ancient Astronauts.
- A variation shows up in Undercover Brother, when Eddie Griffin learns from "The Brotherhood" that all the supposed conspiracy theories about black people are true:
Conspiracy Brother: What do you think? Things don't just happen by accident! Sometimes people — mostly white people — make things happen!
Undercover Brother: So the conspiracies we've believed for all these years are true? The NBA really did institute the three point shot to give white boys a chance?
Conspiracy Brother: Of course!
Undercover Brother: Then the entertainment industry really is out to get Spike Lee?
Conspiracy Brother: Come on man! Even Cher's won an Oscar! Cher!
Undercover Brother: Then O.J. really didn't do it?
[everyone looks away and mumbles]
- The Mummy:
- "Hamunaptra's a myth." ...No it isn't. And no, the cursed mummy isn't a myth either. Although the curator who says that knows very well that Hamunaptra isn't a myth. He is a Medjai who is trying to discourage Evy and Jonathan from looking for Hamunaptra.
- The sequels add the Scorpion King and the Dragon Emperor.
- Hook is based on this as well. That's far less "all myths are true" as it is "those books that were written are true; I know because I'm the one that experienced it, and told the stories to the writer."
Wendy: The stories are true! I swear to you! I swear on everything I adore. And now he's come back to seek his revenge. The fight isn't over for Captain James Hook. He wants you back. He knows that you'll follow Jack and Maggie to the ends of the earth and beyond. And by heaven, you must find a way. Only you can save your children. Somehow, you must go back. You must make yourself remember.
- In Hellboy II: The Golden Army all of the backstory of the titular Golden Army is presented as a legend Hellboy was told as a child.
- Zig-Zagged in Memories of Murder. The local children have an urban legend saying the school outhouses are inhabited by a serial killer. The police learn about this early on in the film and ignore it, but later on, getting desperate to find the killer they're hunting for, they decide to take it seriously and investigate the toilets. They don't find a a murderer there, but they do find an important clue — a crying woman who lives above the toilets and turns out the be the killer's only surviving victim.
- In Alternate Routes by Tim Powers, there's a story several of the characters have heard about a man who was driving on the Los Angeles freeways in the 1960s when he drove off an exit that hadn't been there the day before and wasn't the day after, found himself in the afterlife, and eventually made it back to the world of the living with a mysterious artifact. The story is true; the protagonist eventually meets the man, who helps him figure out what's going on.
- The Stephen King novel Desperation tells the legend of why an old mine was abandoned (a trapped Chinese Laborer summoned a bad spirit). There really is a monster, though actually they just Dug Too Deep and set loose an Eldritch Abomination.
- In Guardians of Ga'Hoole, The Band set out to find the Guardians of Ga'Hoole, which are a legendary group of owls. They are real and eventually The Band join them.
- Harry Potter
- In Harry Potter and the Chamber of Secrets, the legend of the eponymous Chamber, which Professor Binns tells to his History of Magic class and dismisses as a preposterous myth, turns out to be absolutely true, including the deadly guardian.
- In Harry Potter and the Deathly Hallows, the 'Tale of the Three Brothers' is an exaggerated and mythified version of the truth. Justified since they're exposed to the story by someone who already knew it was true.
- Ignite The Stars: Knives tells the cadets a story about an star system called Fugue, abandoned because of a mysterious monster. Ia doesn't think it's real, and neither does Knives. While there isn't a monster, Fugue is a real place, where the Commonwealth has a secret portal gate called GodsEye.
- In Earthsea the myth of human-dragon hybrids trapped in human form, mentioned at the beginning of Tehanu, is proven true at the book's end and forms the basis for the plot of the next novel, The Other Wind.
- In The Eyes of Kid Midas, the teacher explains that the mountain they're camped out underneath is called the Eye of God, and some ways away down in the valley there's a tall, thin spire that's known as the Devil's Chair. According to legend, the peak of the Eye of God was the place where the world was created, and once a year, the very tip of the mountain's shadow falls exactly at the peak of the Devil's Chair. Though the teacher admits it's merely a legend (and the mountain's shadow actually never goes near Devil's Chair), Kevin climbs the mountain, and at the top he discovers a pair of sunglasses that allow him to harness the forces of creation. And lo and behold, when he puts them on, he sees the shadow fall exactly where his teacher said it would.
- In Erika Griffin's novel, The One Who Waited, Alice ponders this during the course of the story, as she comes to realize that there are such things as Boogeymen and wonders if other monsters might exist as well.
- In Anthony C. Gilbert's Farther Up and Farther In All Myths Are True about life after death. Except, apparently, the belief that there isn't any, because the narrator is an atheist but gets sent to Hell, the Christian afterlife being the default for Westerners without other positive beliefs. Escaping from Hell (!) leads to a Crossover Cosmology where he meets Freja, Pan, Monkey and others: the final message (logically, given the opening premise) is that All Gods Are One and we are One with them.
- In the Tales of the Five Hundred Kingdoms by Mercedes Lackey, all fairy tales, from Russian to Middle Eastern to the Brothers Grimm and anything else, are true. In fact, a magical force known as the Tradition actively works to try and make them come true. Those that are Genre Savvy will use the Tradition to their advantage.
- The Bifrost Guardians by Mickey Zucker Reichert is another all myths are true, with the melding of technology to Norse myths to Christianity.
- In Prince Caspian from The Chronicles of Narnia: Caspian was always taught that the "old Narnians" were myths and fairy tales, then he learns that they are in fact real. The appearance of the Pevensies and Aslan also turns out to be this for many old Narnians.
- In Orson Scott Card's The Lost Gate the Westillian Families are the basis of all Indo-European pantheons. It is inferred that other cultures deities, including the Abrahamic one have similar origins.
- In The Kingkiller Chronicle, every single story told in Kvothe's narration turns out to be relevant and mostly true sooner or later; for example, Hespe's story about the boy who loved the moon is a more or less accurate representation of how the mortal world and the fae world ended up going to war.
- The myths and stories of The Cosmere usually correspond to some facet of the magical or historical landscape, so to speak. The local Shards, for instance, are usually major players in the local mythology, and their stated aims and behavior are recognizably in-character. This is clearest when comparing the religious doctrine on Nalthis (of both major factions, no less, as disparate as they are in almost every other respect) to a character's memories of being returned from the dead, but the examples are too numerous to list here.
- The Diogenes Club story "Richard Riddle, Boy Detective in 'The Case of the French Spy'" begins with the Kid Detective protagonist, on holiday in a seaside town, being warned away from a seaside cliff with a local legend that its erosion is caused by angry "sea ghosts" coming out of the ocean at night and clawing away at it, trying to bring down the house built on the clifftop. Later in the story, he also hears another legend about a strange-looking man who was found on the shore near the cliff during the Napoleonic Wars, and was arrested by a guard patrol as a suspected French spy. It turns out that the "sea ghost" legends are inspired by real ancient Fish People who live off the coast, one of whom was the "French spy" who was captured during the Napoleonic Wars and has been held captive ever since in the house on the clifftop. It's not established whether it's literally true that the captive's people have been undermining the cliff, but in the circumstances it wouldn't be surprising.
- In Zodiac, every House has a story about the Thirteenth Guardian, Ophiuchus. While none of them mention him by name, it's clear that all of them are connected. The Libra tale in particular serves as Foreshadowing that the Original Guardians got the wrong culprit, with the real villainAquariuswalking free.
- Averted in Babylon 5's episode "A Late Delivery From Avalon"—an arrival on the Babylon 5 station claims to be King Arthur, brought back among humanity after a long hiatus (when he was "taken to Avalon" on a mysterious "ship"). There is actual discussion among the main characters as to whether this could be true, since there was already a known case where the Vorlons did abduct a historical figure and used him to do their bidding in other times ( "Comes the Inquisitor"). But it turns out he was from the present time, suffering trauma-induced delusion from being the officer who fired the first shot that started the Earth-Minbari War years ago.
- Game of Thrones: It becomes pretty obvious what Bran's dreams really are when Maester Luwin tells Bran that sure, there are stories about people who can form a spiritual link with animals, but they aren't true and would be long gone even if they were.
- MythQuest: Minokichi's mentor tells him the campfire story of Yuki-Onna, an ice demon. Guess who shows up later?
- Seeing as how it's a show with time travel and aliens, this trope is practically a requirement in Doctor Who: every time the Doctor visits a place— real or fictional— with a famed historical/mythological legend surrounding it, you can guarantee that it heavily involves both the Doctor and whatever monster he has to fight this time. Hell, this extends to the point where the extinction of the greater dinosaurs was the doing of one of the Doctor's enemies.
- Ace Combat 5: The Unsung War: A Maybe Magic, Maybe Mundane variation occurs with Wardog Squadron and the legend of the mythical demon of Razgriz; a malevolent being said to rain destruction upon the land whenever history "witnesses a great change", until eventually dying and resurrecting after a period of time... as a great hero. As the plot progresses, it becomes clear that each stanza of the poem narrating said legend — shown in loading screens — thematically corresponds to Wardog Squadron and its role in the Circum-Pacific War.
Amidst the eternal waves of time
From a ripple of change shall the storm rise
Out of the abyss peer the eyes of a demon
Behold the Razgriz, its wings of black sheath noteThe demon soars through dark skies
Fear and death trail its shadow beneath
Until men united wield a hallowed sabre
In final reckoning, the beast is slain noteAs the demon sleeps, man turns on man
His own blood and madness soon cover the earth
From the depths of despair awaken the Razgriz
Its raven wings ablaze in majestic light note
- The Game Boy game Final Fantasy Legend II avoids this. One world your characters explore has a myth that turns out to be true and another myth that turns out to be false. Also, there are actually 78 "MAGI", not just 77 as mentioned at the beginning of the game.
- In Paper Mario: The Thousand-Year Door, Professor Frankly encounters conflicting theories on the nature of the treasure he's looking for.
- Eventually one of the theories turns out to be true: the treasure is an ancient demon. But later it is revealed that the 'real' treasure was a Dried Shroom, the weakest healing item in the game.
- Which really isn't very surprising when you consider it was rotting for the past thousand years.
- In the same district of Rogueport that Frankly's house is located in, you can find a quirky storyteller who is glad to spin all sorts of old stories. But that tale about the horrible evil monster and the four heroes who fought it before being themselves sealed away couldn't be true, right? Of course it is. The monster is a demon sleeping underneath Rogueport right now and Mario actually encounters each of the heroes in the form of talking cursed treasure chests. They're pretty nice.
- In the Shadow Hearts series all myths are true, though very often in ridiculous, bizarre and over the top ways.
- In pretty much all the Final Fantasy games, if you talk to any random NPC who tells you about some legend, the legend is bound to be true. Hidden magical weapons? Yup. Super-powered monsters? Yup. Maze-like hidden cities? Yup.
- In Kingdom Hearts II, there are The Seven Mysteries of Twilight Town, urban legends which invariably turn out to be for real when Roxas investigates (and serve as clues to the nature of the world he's been living in). But when Roxas's friends come along to do the write-up, they assume each was just a misunderstanding of something mundane.
- Bungie's Marathon series contains an interesting example. The second game has a single terminal midway through the game that references a S'pht creation myth where the god Yrro flung a chaotic being into the star that Lh'owon orbits. This terminal is never mentioned by any character for the remainder of the game. The myth then forms the entire plot of the third game, Marathon Infinity — sure enough, the Jjaro (or Yrro) trapped an Eldritch Abomination inside the system's star. Which the Pfhor destroyed in the finale of the second game.
- In Pokémon, any myth or legend you hear about from an NPC is almost guaranteed to be a hint as to where to find a particular Legendary pokemon.
- A set of daily quests in World of Warcraft has you investigate myths about three maidens who will grant powerful swords if you do each a favor. Naturally, all three of them turn out to be true.
- The Goblin starting area also has a mine with pygmy rock art. The rock art depicts a warning about a cataclysmic explosion. Turns out the pygmies have been made smart(er) by the kajamite in the mine, and their warnings are totally correct. Also they worship the creature that lives in the volcano and have captured Horde soldiers to sacrifice to it.
- In Borderlands, the person who sends you to kill Crawmerax the Invincible says that most people think he is a myth and doesn't really exist. Naturally, when you get to the designated spot, he shows up. Subverted in that the quest-giver is quite surprised that you actually managed to find and kill Crawmerax since he made the whole thing up off the top of his head just to mess with people.
- Funny subversion in Lufia: Curse of the Sinistrals remake. At one point you're sent to find the legendary sword, which the legends claim to have been forged by the gods and able to cut mountains in half. Just one line after that you're informed that all of that is just legend, and the sword itself is probably not even magical, but that you should get it just to boost the morale of the people. It turns out that the myth really wasn't true... but the sword is still good enough to be useful by the time you get to it.
- In Star Wars: Knights of the Old Republic, you can learn about the creations myths of the Selkath and the Tusken Raiders. It turns out that both are true and are references to the Rakata, the creators of the Star Maps.
- In Dwarf Fortress Adventurer Mode, if someone talks to you about some dragon who razed his hometown long time ago or a forest where the dead are said to rise and stalk the living, you can be absolutely sure he's telling the unvarnished truth. The only exception to this trope are centaurs, chimeras, and griffons, who sometimes appear on engravings but don't exist in the game world... yet. What's more, the stories will be told with impeccable detail. A thousand years on, everybody in the world still remembers which particular tooth was knocked out of the mouth of a random peasant by a marauding Bronze Colossus.
- In The Legend of Zelda: The Wind Waker, the intro cut scene with the story of the hero of legend and the kingdom of Hyrule turns out to be entirely relevant to the storyline, and last part of the game mainly takes place in the now flooded kingdom. Similarly, all those rumours about the 'triumph forks' turn out to be about the Triforce of Courage that Link finds in the endgame.
- The Legendof Zelda Breath Of The Wild also starts with a myth about Calamity Ganon, which the heroes must use to fight him in the present day. Of course it turns out to be very accurate indeed, although missing a crucial bit of information.
- The Elder Scrolls:
- The Elder Scrolls III: Morrowind plays with this trope, in that the particulars of a certain historical event relevant to the main plot of the game are recounted differently by different parties.
- Played with humorously in The Elder Scrolls IV: Oblivion where Sheogorath asks you (or you ask yourself if you've become Sheogorath) to fulfill a prophecy a small village has about the end of the world that includes attacks by rats and FLAMING DOGS DROPPING FROM THE SKY. The prophecy is used as little more than a prank.
- Some of the local legends recounted to the protagonists of Chrono Cross are correct but... slightly skewed.
- The entire story/legend of the Zeekeeper in Mario & Luigi: Dream Team. You see a ton of exhibits and signs talking about an ancient guardian of the kingdom that saved it from harm, and well, you should probably have figured out pretty quickly that said figure turns out to be a very important character in the storyline and that he helps you take down the Big Bad.
- In Fire Emblem: Path of Radiance, the heroes learn that a medallion holds a dark god who will bring The End of the World as We Know It if freed, and it can be freed by Magic Music or a huge war. The fact that certain people can become mindless berserkers by wielding the relic reinforces this belief. But in the sequel, Fire Emblem: Radiant Dawn, it turns out to be a lie spread by the Dragon Laguz king in vain hopes that it'll prevent war between everyone in Tellius. In truth, endless war will actually awaken the goddess Ashera, who will see the wars as a sign that those living in Tellius are failures, and must be purged away to allow for a perfect world.
- In Jay's Journey, there's a subversion and a straight example. The opening crawl tells a story from the past that has nothing to do with the rest of the game. However, later in the game, Pixie tells the heroes about how the apparent Big Bad, Antignarot, inadvertently got his powers from a demon named Xanabas. Xanabas later becomes a major villain and the Final Boss.
- In Kingdom of Paradise, there is "The Forbidden Poem", which got its name because people feared that learning or reciting the poem would bring disaster. It is a beautiful poem. But the poem is about the existence of the Celestial Twins and their role in opening the Toshintetsu and the gate to Seima.
- In BoxxyQuest: The Gathering Storm, you can buy a storybook that contains heavy foreshadowing disguised as myths and fairy tales. Specifically, it has stories about the duel between Virtua and Legion, the Sky Queen searching for her master, and Lady Nyagai abducting children, although none of the characters are actually mentioned by name. Theres also a hermit who will tell you more about Legion long before he becomes relevant to the plot.
- Nine Hours, Nine Persons, Nine Doors spends a lot of time having characters tell you about Allice, an Egyptian mummy that was being transported in the Titanic. June believes that the ship sank because of Allice's curse, and Seven and Ace add to the legend with their own bits of info. Near the end of the game, you find the coffin where Allice was being carried, you open it... and you find nothing but a key and an emblem, both used to solve a puzzle. Allice is just a way to talk about ICE-9, which is tied to the morphogenetic field, which is a powerful theme in the game.
- Digger spends more than a few strips explaining the hyena mythology surrounding their progenitor-gods "He-Is" and "She-Is", and the "badness" that came from their interactions with the demonic Sweetgrass Voice. Naturally, it's eventually up to Digger to Set Right What Once Went Wrong.
- In The Adventures of Dr. McNinja, if anyone mentions anything unusual or absurd-sounding — like giant lumberjacks, dinosaur-riding bandito paleontologists, zombie ninjas, or the ghosts of dead NASA astronauts — you can bet it'll not only exist but have a direct impact on the plot of the current arc.
- Myths and superstitions in Tales of the Questor tend to be problematic after a few too many generations. Some of them end up being accurate, but for each one that actually is, you've got a few dozen that are corrupted from translation issues or pure age, and hundreds that are plain false or started up from illogical premises. It's also a rule for the setting that no one can see the future, so prophecy tends to always be wrong.
- This short story from Skin Deep. "How am I supposed to know what is actually fiction around here anymore?"
- In 8-Bit Theater, Blue Magic is considered to be the "holy grail of wizardry", and the seven documented attempts at it ended in explosive failure. Then Black Mage gets the power of Blue Magic thanks to a God of Evil... and it turns out to be a massive disappointment.
- In Phaeton if a myth isn't true already then it can become true through the power of the Enigma. Sometimes mythical versions of creatures who already exist become true, that's when things get complicated.
- Scooby-Doo plays this trope for laughs. Typically, something spooky is going on, but is actually engineered by someone wanting to scare people away. Half the time, it's an Invoked Trope, as the fake monster is based on an old local legend (or, occasionally, the villain makes up a story and claims it's an old legend). Once in a while, there's some evidence of actual spookiness, which the heroes may or may not see.
- Jackie Chan Adventures plays this for laughs in an episode about Stonehenge. Apparently, it has some sort of great magical powers, but nobody really knows what it does. Jackie Chan, upon being told this, sarcastically remarks "Yeah, and some people think it's used to contact aliens." The bad guys figure it must be some kind of weapon, and Jackie Chan goes into action to stop them from activating it. Amazingly, the bad guys actually succeed at pulling off their Evil Plan to activate Stonehenge, revealing to everyone present that Stonehenge does... absolutely nothing. Everyone goes home, and then, in the last scene of the episode, a UFO lands at the now-deserted Stonehenge.
- Kim Possible. Mystical Monkey Power is all about this trope.
- He-Man and the Masters of the Universe (1983) does this constantly. Anything that's supposedly just a myth, turns out to be real. EVERY. SINGLE. TIME.
- The Real Ghostbusters and its Sequel Series Extreme Ghostbusters follow this trope pretty faithfully:
- It's subverted in one episode of The Real Ghostbusters, where the Ghostbusters must deal with a creature from Irish folklore. According to legend, the creature can only be stopped by a Four-Leaf Clover. All the characters go out searching for one, except Egon, who, playing the role of Agent Scully, insists that the creature can be captured using the same "scientific" methods they always use. In the end, the four-leaf clover fails (it was a fake taken from a parade float), and Egon saves the day by capturing the creature "scientifically", exactly as he said he would.
- Ben 10 devoted an episode to the Navajo legend of the Yenaldooshi, as told by one of Max's former teammates. The monster in question is indeed real, although it turns out the legend got a lot of things wrong and it was actually an alien.
- Futurama: the in-universe legends of mutants living under the city and El Chupinebra turn out to be completely true — as does the more common myth of crocodiles in the sewers.
- In ThunderCats (2011), the Catfolk-populated magical kingdom of Thundera, stuck in Medieval Stasis, considers technology to be mythical. Stories of "ships that could fly" are fairy tales told to cubs. The populace has become similarly skeptical of the existence of the Book of Omens and Mumm-Ra. In the space of one night, protagonist Lion-O and the Thunderians see their kingdom ruined when old enemies the Lizards invade, bringing with them futuristic technological superweapons, given them by Sorcerous Overlord Mumm-Ra. Lion-O and his Thundercats are then sent on a race to find the very real Book of Omens before Mumm-Ra can get his hands on it.
- The first episode of My Little Pony: Friendship Is Magic has a Storybook Opening of the tale of "The Mare in the Moon". Despite being referred to as an "old ponytale" by others, Twilight Sparkle believes the legend has a basis in reality and is concerned by prediction of Nightmare Moon's escape from her imprisonment on the moon, which is scheduled to happen within days. Of course it's all absolutely, literally true, and the return happens exactly as predicted. Later episodes feature novels starring Indiana Jones Expy Daring Do, initially thought to be a Show Within a Show but later also revealed to be Real After All.