Prior to production, Val Kilmer lived and breathed Morrison for nearly a year, dressing in his clothes and hanging around at his old haunts on Sunset Strip. Jim Morrison biographer Jerry Hopkins says that he saw him one day when meeting Oliver Stone for lunch, using a payphone in the restaurant, and was so convinced by the believable image he cut that the first thought that entered his head was, "I'd forgotten how tall Jim was."
Jim Morrison's real grave is shown at the end of the movie, filmed at the Père Lachaise Cemetery in Paris, France. The headstone has since been changed, and the graffiti was removed from the surrounding graves at the request of Jim's parents. The bust of Jim was stolen sometime in 1988. The grave is also surrounded with a steel fence to prevent further vandalism to the tomb, as pieces of the stone had been chipped off and stolen over the years.
Billy Idol's role was originally much bigger. Prior to filming, Idol was in a motorcycle accident that left him unable to walk. Every time he appears in the film, he is either on crutches, sitting, or lying down.
Because the film was shot out of sequence, Val Kilmer had to carefully gain weight for Morrison's fatter, later years so that the flab was only noticeable on his belly and could be concealed when he played Morrison as a younger man.
The cave scene, when Jim wanders out in the New Mexico desert, was shot at the Mitchell Caverns in the East Mojave Preserve in California. According to the tour guide there, Oliver Stone and the art dept. painted Indian petroglyphs at the site that wouldn't wash off. The state fined Stone and banned future film shoots at the caves.
When Jim is being photographed, he stands in place and looks at the camera as a newspapers and magazines fly by, showing The Doors' rise to fame. A sculpture of Alexander the Great appears over Jim. Jim Morrison compared himself to Alexander the Great several times in his life.
In the film, the band is signed after being fired from Whiskey-a-Go-Go. In real life, they were signed by Elektra Records on August 18, 1966. Whiskey-a-Go-Go fired the band on August 21, after Morrison used acid induced, profane, Oedipus Rex lyrics.
Robbie Krieger, the guitarist in the Doors, gave his consent and assistance to the film because Stone's earlier film Salvador (1986) was one of his favourite films and he could easily envision a film like that about the Doors.
The bar that Jim and his buddies frequented in the movie is Barney's Beanery, a popular spot in W. Hollywood, California. It was the last place Janis Joplin visited before she died at a nearby hotel later that night.
Prior to the audition, Val Kilmer memorized the lyrics to all songs written by Jim Morrison. He also sent director Oliver Stone a video of him performing a few Doors songs, which Stone claimed hurt Kilmer's image as Morrison.
The graves in Père Lachaise that are shown before Jim's are, in order, Frédéric Chopin, Georges Bizet, Oscar Wilde, Sarah Bernhardt, Honoré de Balzac, Marcel Proust, Gioacchino Rossini and Molière. All had careers that were representative Jim's career and interests: Chopin, Bizet and Rossini were musicians. Balzac, Wilde and Proust were writers and philosophers. Berhardt and Molière were live stage performers.
The poem that Jim Morrison is reading at the opening of the film is actually two selections from his book of poetry "An American Prayer": "Awake Ghost Song" and "Awake". It is the same book that Jim gives to his bandmates at the end of the film. However, the musical version of An American Prayer was not recorded by the surviving members of the Doors until several years after Morrison's death.
Jim Morrison (Val Kilmer) is frequently linked with and even directly called Dionysus throughout the film. In Alexander (2004), Kilmer plays Philip, whose wife (Angelina Jolie) is a devout worshiper of Dionysus.
Oliver Stone's then-wife Elizabeth is mentioned in the closing credit roll as Naijo No Ko. This Japanese term means "with the help of my wife" or, more colloquially, "I owe my success to my better half."