“You talkin’ to me?” in Taxi Driver
There’s a scene in Taxi Driver where Travis Bickle (Robert DeNiro) is looking at his awesome body in the mirror. All the while, he’s muttering to himself before he says the infamous quote, “you talkin’ to me?”
Maybe the screenwriters were feeling lazy or Martin Scorsese had tremendous faith in the tremendous actor, but the script didn’t have any dialogue for Robert. So, he ad-libbed the entire scene and came up with that incredible line on the fly. Since then, “you talkin’ to me?” has been parodied everywhere, including in Hey Arnold! Why write a script when you can have legendary actors come up with classic lines?