Screenwriter Scott Rosenberg created the distinctive slang-based vocabulary used by the characters in the film by mixing Vietnam slang and biker slang, and adding in some of his own original diction.
Scott Rosenberg wrote the script in two weeks. It was partly in reaction to the death of his father from cancer.
Film title is taken from a Warren Zevon song of the same name, from his 1991 release "Mr. Bad Example", Zevon wasn't happy with the movie being named after his song, Miramax rectified it by paying him, and the song appeared in the film during the end credits.
According to Jenny McCarthy-Wahlberg during an interview on Late Night with Conan O'Brien (1993), Christopher Walken "smelled like formaldehyde" and nibbled from an apple that had turned brown which he kept in his pocket.
The character name "Jimmy the Saint" is taken from the 1973 song "Lost in the Flood" by Bruce Springsteen.