When characters are mistaken for the beings of another world. If you travel through time
(especially to the mid-20th century or thereabouts) or are an astronaut, this will probably happen to you at least once.
Yet another variant of Mistaken for Index
- Rena from Higurashi no Naku Koro ni mistook her friends for aliens in "The Atonement" chapter. Of course, she was at best, at lv.4 Hinamizawa Syndrome.
- One episode of Ouran High School Host Club had Honey's younger brother Yasuchika accuse him of being an alien simply because he eats three cakes at once in less than a second once a week.
- Franken Fran helps an actress who has fallen for a male lead who is obsessed with anime features, and wants to star opposite him in live-action adaptations. She insists on ever more extensive surgery but fails to take Fran's advice at the hazards in her rush to bed the actor, and cosmetically falls to pieces. He flees in terror, then goes on so many talk shows raving about Grays trying to abduct him that he doesn't get any more roles.
- A running gag in Shinryaku! Ika Musume - Cindy Campbell and her colleagues are convinced that Ika Musume is from outer space, and they would very much like her to visit their laboratory.
- The Teenage Mutant Ninja Turtles do this on purpose in the third Mirage comics volume; aliens having openly made contact with Earth, it's apparently easier for people to accept that than homemade mutant freaks.
- In Spider Robinson's The Free Lunch, when the protagonists notice that there's something very odd about some of the attendees at the theme park where they live, their initial deduction is aliens. This being Spider Robinson, however, they're actually time travellers.
- Take Me to Your President by Leonard Wibberley was about a fellow nicknamed "A-1" from a small British town called Mars, who accidentally got loaded into an experimental rocket. When it landed somewhere other than it was expected to, and he came out wearing the space suit he'd found and saying he was from Mars, well....
- In Amy Thomson's The Color Of Distance has the protagonist, Dr. Juna Saari, spend five years among the alien Tendu, who give her a moist color-changing skin and internal linings that keep her hair from growing and let her breathe particulates and eat foods which she'd normally be lethally allergic to. When humanity comes back to pick her up, the first contact is with a suited man who thinks she's one of the Tendu, and she plays along for a bit before saying "I believe the line is 'Dr. Livingston, I presume?'"
- Christine Peacock sees mysterious lights in a field near the vicarage in Aunt Dimity Digs In, and she's convinced she saw aliens land there. She's even more convinced when a circle of trampled-down grass is found on the spot the next morning. In fact, Sally Pyne and one of the archaeology students were exercising there at night, mostly because Sally was embarrassed to be seen exercising.
- A long-running plot point of Animorphs. The Yeerks thought the kids were Andalites.
- "Tomorrow is Yesterday" from Star Trek: The Original Series.
- The I Dream Of Jeannie episode "U-F-Oh Jeannie", where Tony was mistaken for a Martian by a group of rednecks in the Deep South.
- In Kyle XY, Josh Trager claims, half-jokingly, that Kyle is an alien. (In fact he's an experimental clone with psychic powers.) Two years later, when Kyle finally reveals his history to the Tragers, he comments that Josh's guess may have been the closest to the truth.
- In the Lost In Space episode "Visit to a Hostile Planet", the Robinsons go back through time to 1947 and are mistaken for aliens when they land on Earth.
- In The Addams Family, the Addams are mistaken for aliens by the military, who approach them claiming to wish peace and asking them lots of questions. As a consequence, The Addams believe the army men are aliens as well (because of their green wardrobe).
- SG-1 deliberately invokes this when they're stranded in 1969, presumably figuring that it's a quicker explanation than the actual one.
- Quicker, maybe, but the main reason was to avoid paradox. (Although that didn't stop Jack from going by the names of fictional characters, some of whom already existed and others didn't, but who cares? They didn't want to endanger the Stargate program by accident.
- Averted in the TV Show, Community. Abed plans to 'mess with' Troy by using the classic sitcom set up for this, except that he didn't fool Troy for a second.
- Done in the Torchwood episode "Countrycide", where the team thinks that some aliens are responsible for disappearances and attacks. Turns out, it's a bunch of humanitarians.
- After Yuri Gagarin became the first human to enter space and return successfully, a woman who saw his capsule land asked him "Can it be that you have come from outer space?" He replied "As a matter of fact, I have!"
- Most likely apocryphal, since it's now known that he actually bailed out of his capsule, and wouldn't have landed near it.
- Similarly, when John Glenn was orbiting in the Friendship 7 in 1962, the mission planners weren't exactly sure where the capsule would land - somewhere near Australia, as in any part of Australia or the surrounding oceans or islands for a pretty far distance. Glenn was worried what the aboriginal Australians might think when seeing a man in silver emerge from something that fell from the sky so he took a short speech with him rendered phonetically: "I am a stranger. I come in peace. Take me to your leader, and there will be a massive reward for you in eternity."