Henry B. Dawkins, who plays Billings the X-Ray Technician, really was an X-Ray technician. In the 1990s he became head of the Radiology Department at Asheville-Buncombe Technical Community College in Asheville, North Carolina, one of this film's shooting locations.
In different versions, the end credits are either shown over retakes of Chance saying a line that was not in the movie (the message from Raphael, restored to the home video version) or shown over TV white noise. Peter Sellers was at the film's screening at the 1980 Cannes Film Festival and was furious with director Hal Ashby and the producers for including the outtakes version of the end credits at this performance as well as the audience's reaction to them. This incident may have finally made the producers change their minds. When the film opened soon after in Australia in late May 1980, the entire end credits were removed from all prints (leading to a deafening thud on the soundtrack after the film's final line). These prints were all replaced with versions including the "white noise" end credits, including the film's main theme by composer Johnny Mandel.
Originally there was a different last shot planned for the funeral sequence at the end of the film. Director Hal Ashby was chatting with another director one day about filming when he commented how well everything was going. "It's like walking on air," he said, then suddenly was struck with a thought. He changed the last shot to the one that appears now in the movie.
Peter Sellers was nominated for the Oscar for Best Actor. Some said the reason Sellers lost was because of the outtakes at the very end of the movie as the credits are rolling. Sellers himself later said the outtakes "broke the spell" of the movie.
After the novel's release and the subsequent purchase of rights to the book, Peter Sellers successfully lobbied for the lead role by sending a telegram to author Jerzy Kosinski with the message, "Gardener available for work". It was during casting and after the success of the later Pink Panther movies that Sellers became the only choice for the lead role.
When the gay partygoer, who thinks Chance has suggested his interest in watching gay sex, says "You wait here: I'll go get Warren," this may be a dig at 'Warren Beatty'. Beatty's heterosexual activity was legendary, and the professional and personal relationship between him and Hal Ashby was at times virulent, with Ashby refusing to see Beatty during the waning months of his life.
Every contract that Peter Sellers signed included a clause which stipulated that his accommodations must have the bed facing East-West. Chance says: "I like to sleep with my head facing North". The attorney he's with says "But this bed is facing west!"
It took Peter Sellers nearly nine years to get this movie made by a studio, mainly because by the 1970s Sellers' career had hit rock bottom and no studio in Hollywood would work with him. After the revival (and success) of the Pink Panther movies, Lorimar Pictures finally greenlit the project.
In the scene where Chance decides to try kissing Eve, he is watching The Thomas Crown Affair (1968) from 1968 on television as his example. Hal Ashby, the director of this film, was the editor of that film.
The trivia items below may give away important plot points.
The South African Publications Control Board ordered that the final minutes of this film be cut from the South African release print as the scene showing Chance walking on the water surface "might offend many South African Christians".
The inscription "Life is a state of mind" is on Rand's tomb and also serves as the last line in the movie. These words were also inscribed on Peter Sellers' own tomb, when he died a year after the movie was released.