Accidentally choosing the evil twin

Well as the title says, can you guys help me find any media where there is a character who has to choose between 2 people, one real and one being an impostor, both claiming to be the actual person and trying to prove themselves as the real one with personal anecdotes or inside jokes so that they don't get caugth or killed or arrested? I can think of a couple of examples, like the ending of pretty little liars or that one episode of Gravity Falls where Wendy has an evil doppelganger, but I don't know any where the character who has to make the decision ends up picking the wrong person. Any suggestions, even if they are major spoilers, are well appreciated.