I have never seen an actor as dedicated, with the extreme concentration and exceptional imagination as James Dean. He could take the written imaginary circumstance and make it his own by improvising - lying on the ground in a fetal position playing with a wound-up toy monkey beating its cymbals, giggling while being searched in the police station because it tickled, standing up in a drunken daze making the sound of sirens with his arms outstretched, hitting his fists into the sergeant's desk, jumping off a diving board into a swimming pool with no water, or doing the voice of Mr. Magoo throughout the movie, which was the voice of Jim Backus, his father in Rebel - things that were not written on the page, things that were invented by the actor.