OP note: I asked before and apparently we don't have this one, so here's a YKTTW for it.
Good friends know each other very well, sometimes they may know each other better than they their respective friends may know themselves. In some cases too, friends' quirks, habits, characteristics, and such may also rub off on each other. Then you have cases where the friends will start to act like each other, either by intention, or unintentionally; whenever this happens, expect hilarity to ensue
, especially when those around them are dumbfounded by what's going on.
Not to be confused with "Freaky Friday" Flip
, where the two parties find themselves literally in each other's bodies.
- Seinfeld. In "The Chicken Roaster," Jerry and Kramer switch apartments as Kramer is unable to sleep with a giant red neon chicken glowing across the street from his window; afterwards, Kramer begins to act more like a cynical Jerkass like Jerry, while Jerry stays up talking to people like Bob Sacamanno and Lomez and mooching food off Kramer much like he did. Both George and Elaine are a little weirded out by this.
- Arthur. In "Buster's Best Behavior," Buster feels inferior because he doesn't really stand out among the crowd and decides to try and be more like someone he admires, namely Arthur. Meanwhile, Arthur feels Buster is the coolest kid in school and decides to try and be more like him. Soon, Buster is walking around in yellow sweaters, reading lots of books, and complaining about D.W., while Arthur is constantly snacking and reading joke books, causing the two to quickly become bored with one another. Brain refers to the phenomenon as "Element X," but both Francine and Muffy are driven crazy.
- Ed, Edd n Eddy. In "Mirror, Mirror on the Ed," the Eds play each other at truth or dare, where at one point, Ed dares Eddy to pretend to be Double D, which prompts Eddy to dare Double D to pretend to be Ed, which he'll only do if Ed pretends to be Eddy. Later, the Eds continue to pretend to be each other for the rest of the day, and each of them Flanderize the other's quirks: Eddy overplaying Double D's use of big words (though turning into a Malaproper in the process) and lack of physical strength, Double D playing up Ed's spaciness, and Ed channeling Eddy's bossy nature. It comes to bite them in the butt later when Kevin tries to pummel Eddy for masquerading as Double D, Sarah mistakes Double D for Ed and forces him to clean up his room, and Jonny daring Ed to pretend to be Plank while Plank pretends to be Eddy.