Two races, or tribes, were familiar with each other's existence a long time ago but they have gone ages without contact with each other, and now each believes the other to be creatures of legend, that either never existed or died out long ago.
Until they meet each other. And they both react exactly the same way: by saying something along the lines of "They do exist!" in a tone of awe. At the same time. (Or at least one directly after the other.)
Compare Mutually Fictional, where the two sides really did originate as (or still are) only stories to each other.
- The Russian advertisements for Hochland cheese:
Son: Dad, do aliens exist?Father: No, son, it's fiction![Cut to an alien planet]Alien son: Dad, do humans exist?Alien father: No, son, it's fiction!
- One classic Christmas ad for M&M's had Yellow checking to see whether Santa Claus had arrived, while Red obviously thought this was a waste of time. However, they run into Santa at their tree, and...
Red: AAHH! He does exist!
Santa: They do exist...
[They both faint]
- In the Bronze Age, we learned that DC's Golden Age Funny Animal comics characters all live on Earth-C (for "cartoon"). The most famous inhabitants are Captain Carrot and His Amazing Zoo Crew! There, humans are considered mythical monsters. A wolf who is cursed to transform into a human is called a Wuzwolf.
- Done jokingly in X-Men. While in Banshee's ancestral home, the X-Men run into leprechauns. When Wolverine expresses his disbelief in leprechauns, one of them retorts "Well maybe I don't believe in talkin' wolverines!"
- In one The Little Mermaid comic Ariel accidentally comes across a city where moray live. Moray were deemed fictional by merpeople. In turn, moray thought merpeople were a myth. Moray are afraid of merpeople. The moray princess decides to keep Ariel as a pet, then ransoms her when she learns that Ariel and her sister Aquata are princesses. Moray are depicted as the Evil Counterpart to merpeople.
- In FernGully: The Last Rainforest, humans have been away for so long that the fairies only remember them through legends and folk tales, resulting in most fairies not even believing in humans until of course a logging company arrives in the area.
- The premise of Smallfoot is that yetis don't believe in humans, considering them a mythical monster they call "smallfoot". Naturally, Hilarity Ensues when the one yeti who does believe actually catches a glimpse of a human on the mountain and heads down to the lowlands to prove they exist. Justified; the eldest of the village, the Stonekeeper, knows that there were hostile encounters between humans and yeti in the past, so he has shaped their entire culture to keep them hidden from humanity due to his belief that Humans Are the Real Monsters.
- In Legion
Bob: You know this is crazy, right? I mean... I don't even believe in God.
Michael: Well, that's just fine, Bob. He doesn't believe in you either.
- Referenced and inverted in The Muppet Movie, in the Electric Mayhem's song "Can You Picture That":
Fact is there's nothing out there you can't do,
Yeah, even Santa Claus believes in you!
- In Through the Looking Glass, when Alice meets the Unicorn, it asks what she is. When told that she is a child, it replies, stunned, "I always thought they were fabulous monsters!" When Alice confesses that she always believed that unicorns were fabulous monsters, the Unicorn says, "Well, if you'll believe in me, I'll believe in you," to which Alice agrees.
- In The Lion, The Witch, and The Wardrobe, Tumnus the faun reacts this way to Lucy the first time he meets her, and owns a book called Is Man a Myth? A rather justified example, since the few humans in Narnia at its creation had been crossbred into oblivion with the other races within the first few generations, a thousand years before his time.
- In J. R. R. Tolkien's Farmer Giles of Ham, younger dragons seem to think that the Knights are just a myth. The older ones know better, although they admit that they are few and far, and not a danger anymore. Which is true. The King and his Knights are pretty useless. The only person who can effectively deal with the Dragon is a fat, red-headed farmer who doesn't like trespassers—even if they are scaly and breathe fire.
- The Monster Bed: When her son panics about the possibility of humans crawling under his bed, Dennis' mother tells him that humans are fictional creatures. At the end, the narrator tells the reader to avoid the Withering Wood, or they might meet Dennis' mother, who would tell them they don't exist.
- The Dragon With the Girl Tattoo, a spoof of The Girl with the Dragon Tattoo.
- The Divide trilogy by Elizabeth Kay has a fantasy world where all kinds of creatures from our myths live. They not only think humans are mythical, but also many animals from our world as well.
- Xanth has humans (although if they didn't get fresh blood from Mundania they'd eventually change into magical creatures), but all of their animals are magical. As such, they think of a horse as a wingless pegasus, a lion as something with a griffin's body and a chimera's head, etc.
- An early portion of The Martian Chronicles has a Martian parent talking to a child, assuring it that there can't be any life on Earth, because of the excessive amounts of oxygen.
- In one of the Garrett, P.I. novels, the protagonist muses that certain creatures of legend don't exist in his Fantasy Kitchen Sink world, being allegorical fictions rather than genuine beings. These include fire-breathing dragons, gryphons, and ostriches.
- In Stanisław Lem's Fables for Robots, most robots either believe that humans (palefaces) don't exist or that they are long extinct. Every time they meet biological lifeforms, they are disgusted by them.
- Three Hearts and Three Lions: the main protagonist is a real-world Dane from World War II who gets transported in a fantasy world where the characters of the Matter of France are historical characters, but where some figures like Julius Caesar and Emperor Napoleon are legendary.
- The dwarven grags of the Discworld (deep-downers, or "those who do not get out in the fresh air enough") believe humans to be a kind of bad dream. This puts them at odds with the rest of the dwarfs, who are quite willing to deal with humans (their mythology even gives a shared origin for humans, dwarves and trolls).
- Magnus Chase and the Gods of Asgard is based on Norse Mythology but in modern times Alfheim and Nidavellir (worlds inhabited by elves and dwarfs respectively), the magic has gone away and humans are seen as mythical creatures confined to fairytales and TV shows.
- Before meeting each other, the Power Rangers (In Space) and Teenage Mutant Ninja Turtles ("Next Mutation" version) each thought the other was an urban legend.
- Which, as Linkara's History of Power Rangers pointed out, is somewhat headscratching, as the Rangers have been well-known public figures for quite some time, to the point that they have been on TV, and there are towns with Monster Attack Preparedness Drills.
- The Star Trek: The Original Series episode "The City on the Edge of Forever" has 1930s philanthropist Edith Keeler understandably skeptical of Leonard McCoy's claims to be a time-traveling doctor from a star ship in the 23rd century. Bones, still in recovery from overdosing on a psychoactive drug, likewise dismisses her as some kind of hallucination he must be having.
- The Outer Limits (1995): This is played with in "Promised Land". Dlavan has always told his daughter Krenn and his grandsons Ma'al and T'sha that all the humans on Earth are dead. However, it turns out that Dlavan knew from his great-grandparents that some of them were still alive in a concentration camp overseen by androids in spite of the fact that most of their people, the Tsal-Khan, left Earth 100 years earlier.
- Humans are so rare in the world of Pokémon Mystery Dungeon: Gates to Infinity that the Pokémon living there believe that humans are only found in fairy tales. That is, until the human protagonist arrives in a form of a Pokémon like in past Pokémon Mystery Dungeon games.
- The Mechanimals in The Day The World Broke only knew about humans within myths and legends, and despite knowing their language, were never aware that anything existed outside their home territory, let alone humans. The only human who ever lived with them was Ozzie Jr., circa 65 million years prior. Having accidentally caused all the prehistoric life forms to be sucked into the World Machine's core during the Great Tune Up, he fled there and fed them food with mechanical parts mixed in, that caused them to evolve into how they are now, up until he died in the magma cavern. By the time the newer breed of Mechanimals dug up his body, nobody but Diode suspected it was really a human. And then you come along when the entire world machinery above goes on the fritz.
- Referenced in College Roomies from Hell!!! when Roger meets two centaurs who think humans are mythical creatures. However, they're actually genetically engineered creatures who have been given this belief (and a steady diet of drugs) by the Evil Genius in question to avoid them questioning their surroundings.
- In Girl Genius, Wooster tells Agatha that the reason the multiple underground societies beneath Paris are considered a "secret", even though everyone who matters knows they exist, is that everyone else simply refuse to believe in them. As they talk, they pass an intelligent carnosaur, who snorts "What?! More of you costumed frauds? How far will the papers go to spread their bogus stories of a 'surface civilisation'?"
- Pops up at the end of the sleepover episode of The Adventures of Jimmy Neutron: Boy Genius. The climax of the episode features a series of increasingly nonsensical Catapult Nightmares involving the various characters and a flying vampiric pizza. The final nightmare turns out to belong to an actual vampire pizza, sleeping in his pizza box; when he explains his terrible dream to his wife, she consoles him that children don't exist, and everyone knows that.
- Kaijudo: The creatures didn't believe humans were real before meeting them.
- Dragon Tales: Before meeting Emmy and Max, Ord and Cassie had only seen kids in fairy tales.
Emmy: You talk!
Cassie: So do you!
- Later, Spike didn't know what Emmy and Max were until Cassie told him they're children.
- In the first episode of The Adventures of Teddy Ruxpin, Gimmick crashes his airship into the tree of Leota the Woodsprite. When she introduces herself, Gimmick says there's no such things as "woodsprites", she quips back that there's no such thing as big bags of air stuck in her tree, yet there it, big as life.
- In one episode of The Lion Guard Bunga believes that Besthe's new okapi friend is imaginary because he sounds like a Mix And Match Creature. When he turns out to be a Not-So-Imaginary Friend and meets Bunga, the okapi says he didn't believe honey badgers really existed, because their smell and looks sounded outlandish.
- In one episode of Camp Lazlo, Raj is mistaken for a yeti, then at the end, it cuts to two yetis with one admonishing the other for being scared because he heard the Squirrel Scouts' yelling, telling him that campers are a myth.
- In an episode of DuckTales (2017), the kids go on a search for a species of underground creatures called the Terra-Firmians. When they finally meet some near the end, the Terra-Firmians are implied to have been engaging in a similar search for the ducks.
- Parodied in "Moon Problems" from Summer Camp Island. A talking ice cream sandwich sees a mermaid and says "Mermaids are real?". One of the mermaids looks equally astonished and says "Woah, ice cream sandwiches are real!".
- The Simpsons: In "My Way or the Highway to Heaven", God doesn't believe atheists exist.