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.
James Dean and Paul Newman were filmed together in a crude screen test in New York that still exists, according to Dean biographer David Dalton in "The Mutant King" (1974). In the screen test, Newman is quite cool and stares straight ahead while Dean is more animated, and is flipping something up and down in and out of his hand like George Raft and his nickel in Scarface. When Dean is asked what the object is, he admits that it is a switchblade, the premier symbol of the juvenile delinquent menace much feared in the 1950s. In an excerpt of the test now available on the Internet, there is no evidence of Dean playing with a knife.
Elia Kazan first toyed with the idea of casting Marlon Brando as Cal and Montgomery Clift as Aaron, but at 30 and 34 years old, respectively, they were simply too old to play John Steinbeck's teenage brothers. Ironically, the youthful-looking Paul Newman, who was one year Brando's junior, was a finalist for the part of Cal, which eventually was played by Newman's friend James Dean. Dean was seven years younger than Newman.
Elia Kazan, in his autobiography "A Life" (1988), said that Raymond Massey came to despise James Dean. Kazan did nothing to dispel the tension between the two, as it was so right for their characters in the film.
Timothy Carey, who had a small part as Joe the bouncer, drove director Elia Kazan to such distraction with his bizarre behavior that Kazan, a longtime avowed pacifist, physically attacked him, the only time he had ever done such a thing.
During the production of the film, Elia Kazan used to write letters to his friend John Steinbeck, with whom he had worked closely on the original screenplay for Viva Zapata!, to keep him abreast of the film's progress. Steinbeck thought James Dean was a perfect Cal, and tremendously enjoyed the final film.