 Travis Bickles famous "You talkin to me?" scene may have been  inspired by De Niros training under Stella Adler (qv), who (as an  exercise) had her students practice different interpretations of a  similar phrase. The legendary acting teacher was surprised to see  one of her former students use "You talkin to me?" as a psychotic  mantra. Martin Scorsese (qv) was encouraging De Niro just below  the camera while shooting the scene, which lead to the rest of the  "dialogue" Bickle has with his mirror.