abyssinia4077 and I were talking about our on-screen pet peeves. Hers has to do with bad science. Mine is any time it calls for a character to "play" piano. Ninety-eight percent of the time (yes, I'm making that up), the hand movements aren't even in the right SECTION of the piano. Even when they don't show the hands, I can tell by body language whether or not the actor is even making an honest attempt.
And don't get me started on music syncing.
So what's your pet peeve? Something you know so well that any little thing wrong jumps out of you and takes you right out of the story?