Before shooting, Gene Hackman and Al Pacino both dressed as hobos and hitchhiked through California to get into their characters.
Gene Hackman's line to the waitress, "Is this your first day?", was an ad-lib. Hackman was genuinely annoyed with the actress.
This film is often overlooked in both lead actors' canon, but it is often cited by both Al Pacino and Gene Hackman as one of their favorite films.