In the scene where Adam refuses to accept Cal's money, the script called for Cal to turn away in anger from his father. It was James Dean's instinct to embrace him instead. This came as a surprise to Raymond Massey, who could think of nothing to do but say, "Cal! Cal!" in response.
Despite the annoyances and difficulties he faced making this film, Raymond Massey called the role of Adam Trask one of the best parts he ever had on screen and one of the few three-dimensional characters he played in movies.
Elia Kazan noted that James Dean's tension and shyness always manifested itself physically, so he allowed the actor to use contorted, awkward postures to convey the character: "It was almost psychotic. He was exactly like the people you see in insane asylums."
Elia Kazan denied rumors that he didn't like James Dean: "You can't not like a guy with that much pain in him . . . You know how a dog will be mean and snarl at you, then you pat him, and he's all over you with affection? That's the way Dean was." Kazan did intervene sternly, however, when Dean started to feel his power as a hotly emerging star and treated crew members disrespectfully.
Upon being introduced to James Dean on the set, author John Steinbeck exclaimed, "Jesus Christ, he IS Cal!"