To get into character, Bill Murray spent time with Thompson, drinking and 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 consternation/annoyance of cast and crew members.
In an early scene, the establishing shot outside a seedy bar contains two seedy characters standing outside it, lighting cigarettes. They are musician Neil Young and music producer David Briggs, who contributed to the soundtrack selection and recording.
In the beginning of the movie (about 15 minutes into it), 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 "Fear and Loathing", which is a tag line of Thompson's.
The character of Carl Lazlo is loosely based on 1960s Chicano lawyer Oscar Zeta Acosta. Acosta was briefly Thompson's attorney during the 1970s and is the basis for the character of Dr. Gonzo in Fear and Loathing in Las Vegas (1998). The title of this movie is an allusion to Acosta's book "Autobiography of a Brown Buffalo".