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.

The character of Carl Lazlo is loosely based on Oscar Zeta Acosta, who was Hunter S. Thompson's attorney for a short time in the 1970s. The movie's title is an allusion to Acosta's book "Autobiography of a Brown Buffalo."

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.

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."

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 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.

The latter two sections of the film are based on Hunter S. Thompson's books and articles "Fear and Loathing on the Campaign Trail '72" and "Fear And Loathing At The Superbowl: No Rest For The Wretched," both published in 1973.

Jack Nicholson, Chevy Chase, Dan Aykroyd and John Belushi were considered to star as Hunter S. Thompson.

Hunter S. Thompson was eventually brought aboard the film's production as "executive consultant", but claimed he had no substantial role other than to have "wandered around and fired machine guns on the set".

Hunter S. Thompson wrote several alternate openings and endings for this movie, none of which were used.

Martin Scorsese briefly considered directing this film with Jack Nicholson starring, but both ended up passing on the project.

This is the first theatrical feature film adaptation of a story written by Hunter S. Thompson.

Bill Murray was the first actor to portray Hunter S. Thompson in a film or television feature.

Hunter S. Thompson met with the film's screenwriter John Kaye, and felt that Kaye understood more than what was in the script, which he described as "bad, dumb, low-level, low rent". Thompson admitted that he signed away script control so he couldn't be blamed for the end result.

Just before principal photography was to begin, Bill Murray became apprehensive about the project because of the shortcomings of the script.

Before principal photography began, Art Linson took a four-month crash course in directing.

Only the theatrical release and early VHS releases contained the songs found on the soundtrack. Because of the high cost of music licensing, all DVD and most VHS releases include only Neil Young's score and the Creedence Clearwater Revival song, "Keep on Chooglin'." The rest of the music is replaced by generic approximations of the original songs.

About 15 minutes into the movie, while Lazlo is dictating to HST in the car, a cop is busting three guys. The wall they are putting their hands on, has graffiti that says "Fear and Loathing", which is a tag line of Hunter S. Thompson's.

John Kaye has claimed that Hunter S. Thompson and Bill Murray changed parts of the script during filming and, at that point, he chose to no longer be involved in the production.

Debut theatrical feature film scored by composer and song writer Neil Young.

In the late 1970s, Thom Mount paid $100,000 for the film rights to "The Banshee Screams for Buffalo Meat," Hunter S. Thompson's obituary of Chicano activist Oscar Acosta. Thompson agreed to have it optioned without seeing a screenplay, figuring that the film would never get made. Thompson's book Fear and Loathing in Las Vegas had been optioned several times before it was made into a film.

Ralph Steadman observed Art Linson on the set and said that it was "pretty obvious that he was in no frame of mind to catch the abandoned pure essence of gonzo madness, which can only happen in uncontrolled conditions". He also felt that Linson's "fanaticism for the subject he was trying to portray was undoubtedly there, and his sincerity, too", but felt that he was under the impression that the film was a runaway hit before he had even begun filming it and therefore refused to take any chances with the material.

Bill Murray and Hunter S. Thompson, concerned about the film's lack of continuity, added voice-over narration in early 1980. When the film was sneak-previewed in late March, the last two scenes and narration were missing. Murray was outraged, and the studio ended up shooting a new ending. Three days before it was to be released in theatres, a press screening was suddenly cancelled because of editing problems.

In the original script, Lazlo's surname was Mendoza. It was changed after Nosotros, a group of Chicano actors and filmmakers, threatened to create controversy if the character was played by European-American Peter Boyle.

Debut theatrical feature film directed by writer-producer Art Linson whose only other directorial credit after this movie was about four years later with The Wild Life (1984) for the same studio (Universal).

The plane used for the "Zoo" is a Lockheed L-188 Electra. By the time this movie was shot, the aircraft was primarily used as a cargo plane.

Hunter S. Thompson, billed as "Dr. Hunter S. Thompson", acted as an executive consultant to the production.

This is one of two Art Linson films released in 1980. The other was Melvin and Howard (1980).

The picture's opening credits declare that the film is "a movie based on the twisted legend of Dr. Hunter S. Thompson".

Oscar Zeta Acosta is known in the film as "Carl Lazlo, Esq.".

Craig T. Nelson: As a cop on a witness stand.