To get into character, Bill Murray spent time with Hunter S. Thompson by drinking, shooting and generally having a great time at Thompson's Colorado ranch. After filming ended, Murray continued to act "Gonzo" through the beginning of the next season of Saturday Night Live (1975), to the annoyance and consternation of cast and crew members.
In an early scene, the establishing shot outside a seedy bar includes two characters lighting cigarettes. They are musician Neil Young and music producer David Briggs, who contributed to the soundtrack selection and recording.
Ralph Steadman, who did illustrations for Hunter S. Thompson's books, drew the title cards for this movie. The closing titles credit Steadman for "Title Splatters", "Gonzo Calligraphy" and "Incidental Artwork".
During production, Bill Murray and Hunter S. Thompson engaged in a series of dangerous one-upmanship contests. "One day at Thompson's Aspen, Colorado, home, after many drinks and after much arguing over who could out-Houdini whom, Thompson tied Billy to a chair and threw him into the swimming pool. Billy nearly drowned before Thompson pulled him out."
During the opening credits, Peter Boyle receives first billing and Bill Murray receives second billing. DVD and video covers, movie posters, and promotional materials tend to give Murray top billing.