 Director George Roy Hill (qv) said that the script was more  serious than the final movie, and during rehearsals,  Paul Newman (I) (qv) played the role of Butch "straight". When  they shot the first scene, where Butch first knocks on the door of  the boxcar in which the safe is contained, he played the scene for  comic effect. Hill approached Newman, and after a chat, it was  decided that Butch would be a comic character. Thus, the whole tone  of the film changed.