Something that is a work of fiction or some people practicing for the real thing gets mistaken for the real thing. Poor Communication Kills comes into play and most the rest of the episode is based on this one misunderstanding. May lead to You Just Ruined the Shot.
While this trope often pops up because of a simple miscommunication it also can turn up in works where there are aliens involved. No Such Thing as Alien Pop Culture, right? Well, Law of Conservation of Detail might explain that, but in this case the aliens literally do not have pop culture. Or any other form of entertainment, because in their culture there is no such thing as fiction. And therefore, when they watch something like Star Trek they think we actually have laser weapons and photon cannons.
This trope does not have anything to do with an ultra-realistic costume or anything of the sort.
Inverse of And You Thought It Was a Game, where something that's real gets mistaken for pretend. Related to Out-of-Context Eavesdropping, This Is a Work of Fiction, Cannot Tell Fiction from Reality, You Watch Too Much X . Similar to Red Herring.
- One episode involves the cast getting ready to fight a bunch of Mole Men after one of them had a premonition that they were invading the surface. Turns out, it was just shooting for a movie.
- The 2015 movie "Nobita's Space Heroes" has the roles flipped: this time, the cast is shooting for a movie and an alien comes to them for help thinking they are superheroes.
- Galaxy Quest. A group of aliens in question believe a TV show is real and thus ask the actor for help in defeating their enemy.
- Night at the Museum: Secret of the Tomb: the Lancelot statue that gets alive ran away from the museum to try to find the kingdom of Camelot. When he finds it, it's actually a theatrical play with Hugh Jackman as King Arthur. Lancelot, knowing nothing about opera, goes onto the stage and talks to "Guinevere" as if she's the real one, which confuses the viewers. When he's told that it's just an opera and not a real thing, Lancelot goes nuts and runs away.
- Pixels revolves around this as the aliens mistake a video game as a declaration of war.
- When the Yeerks first came to Earth, they were horrified to discover that humans not only had variable-setting laser weapons, but were capable of multiples-of-lightspeed travel in realspace (with recording devices capable of such impossible speeds). They quickly figured out it wasn't real, but thought it was for intimidation purposes. It wasn't until they started infesting them that they understood the human need for entertainment.
- The Ellimist's species was destroyed due to a misunderstanding: one of their favorite pastimes was playing extremely detailed Civilization-like games, which were part of the data they broadcasted into space. Another species picked up the signal and saw a race of Manipulative Bastards who played god with other sentient beings, and destroyed nearly all the Ketrans. Ironically, the Ellimist eventually did play games with other sentients when he had attained godlike power.
- Blackadder: In "Sense and Senility", the two actors trying to coach Prince George take a break to rehearse their own play, "The Bloody Murder of the Foul Prince Romero and His Enormously Bosomed Wife" (a philosophical piece). Baldrick overhears them during a scene planning to torture the prince and his servant, thinks it's for real, and the panic spreads to Prince George. Blackadder returns, and immediately realizes the truth, but chooses to get rid of the actors by confirming that they were traitors, having made the classic mistake of planning their deed by writing it in play format.
- Space: Above and Beyond: The Chigs often mutilate human dead out of a mistaken belief that humans can come Back from the Dead. Having no concept of an afterlife themselves, they misunderstood The Four Gospels after stealing cable.
- In Undertale, Undyne believes that anime is human history. When Alphys confesses to her that it isn't, she initially laughs it off, but then begins to undergo an existential crisis. You have the option to either reassure her that it is real, or confirm that it isn't.
- American Dad! episode "An Apocalypse to Remember": Stan mistakes a nuclear drill as real and thinks nuclear war is happening, evacuating his family to the woods. He then spends most the rest of the episode hiding the truth from them so his family doesn't think he's an idiot.
- One episode of The Simpsons had the family go on a cruise. When Bart realizes that the cruise is going to end soon and he'll never have fun like that again, he tries to extend the cruise by passing off a movie about a viral outbreak as a news report. It fools everyone, including celebrity passenger Treat Williams who starred in the movie.
- In one episode of Family Guy, Mayor Adam West watches Romancing the Stone and sends the entire Quahog police force to rescue the film's heroes, but by the end of the episode, the rescue is called off.
- In the She-Ra and the Princesses of Power episode "Roll With It", Scorpia uses a spy-bot to spy on the Alliance's planning session. However, unknown to her, the session has devolved into the Princesses trying to one-up each other with crazy stories about how they'd use made-up powers to single-handily capture the fortress Scorpia is guarding. Scorpia believes everything she hears and is terrified.
- On October 30, 1938 the book The War of the Worlds about an alien invasion was adapted into a series of fake news broadcasts for The Mercury Theatre on the Air, which fooled many people into thinking an actual invasion was happening and causing mass panic.note
- In Dave Barry's Complete Guide to Guys, Dave tells the story of two of his friends who are given the alias of "Wally" and "Lynde" because they were stoned during the story. They were watching TV and the broadcast was interrupted by an news report about Hurricane David, with the couple slowly realizing that they had no time to get ready even if they could think clearly or had full mobility. Fortunately Wally eventually remembered they were watching a recording made several years back, so the danger posed by the David had passed.