The blonde wig that Barbara Stanwyck is wearing throughout the movie was the idea of Billy Wilder. A month into shooting Wilder suddenly realized how bad it looked, but by then it was too late to re-shoot the earlier scenes. To rationalize this mistake, in later interviews Wilder claimed that the bad-looking wig was intentional.
Billy Wilder and Raymond Chandler did not get along well while writing this film's script, a process that was apparently filled with arguments. Wilder claimed that he flaunted his womanizing ability at the time to torment the sexually-repressed Chandler.
In the scene where Phyllis is listening at Neff's door as he talks with Keyes, Keyes exits into the hallway and Phyllis hides behind the door. The door opens into the hallway which isn't allowed by building codes even back then, but it does give Phyllis something to hide behind and increases the tension.
This film came out in 1944, the same year David O. Selznick released "Since You Went Away (1944)." Part of the campaign for the latter film were major ads that declared, "'Since You Went Away' are the four most important words in movies since 'Gone With the Wind'!" which Selznick had also produced. Wilder hated the ads and decided to counter by personally buying his own trade paper ads which read, "'Double Indemnity' are the two most important words in movies since 'Broken Blossoms'!" referring to the 1919 D.W. Griffith classic. Selznick was not amused and even considered legal action against Wilder. Alfred Hitchcock (who had his own rocky relationship with Selznick) took out his own ads which read, "The two most important words in movies today are 'Billy Wilder'!"
The character Walter Neff was originally named Walter Ness, but director/writer Billy Wilder found out that there was a man living in Beverly Hills named Walter Ness who was actually an insurance salesman. To avoid being sued for defamation of character, they changed the name. In the novel, his name is Walter Huff, and Dietrichson is Nirdlinger
Author James M. Cain later admitted that if he had come up with some of the solutions to the plot that screenwriters Billy Wilder and Raymond Chandler did, he would have employed them in his original novel.
Barbara Stanwyck was the first choice to play Phyllis, but she was unnerved when seeing the role was of a ruthless killer. When she expressed her concern to Billy Wilder, he asked her, "Are you a mouse or an actress?"
Raymond Chandler hated the experience of writing the script with Billy Wilder so much that he actually walked out and would not return unless a list of demands was met. The studio acceded to his demands and he returned to finish the script with Wilder, even though the two detested each other.
During production, one day Raymond Chandler failed to show up at work and was tracked down at his home, and he went through a litany of reasons why he could no longer work with director Billy Wilder. 'Mr. Wilder frequently interrupts our work to take phone calls from women... Mr. Wilder ordered me to open up the window. He did not say please... He sticks his baton in my eyes...I can't work with a man who wears a hat in the office. I feel he is about to leave momentarily.' Unless Wilder apologized, chandler threatened to resign. Wilder surprised himself by apologizing. "It was the first - and probably only - time on record in which a producer and director ate humble pie, in which the screenwriter humiliated the big shots."
When "Double Indemnity" was first published in 1935, offers of up to $25,000 were tendered but nothing came of it at the time because the Hays Office considered the novel unsuitable for filming. James M. Cain was ultimately offered $15,000 by Paramount. He was to get half on signing and the other half if the script was approved by the Hays Office.
When approached about adapting the novel to the screen, Chandler told Wilder that he had to get at least $150 a week in salary and was surprised when Joe Sistrom told the writer that they had planned to give him $750 a week.
Chandler, who knew nothing about screen writing or film making had never been in a studio before "Double Indemnity," did not care for Wilder. He thought the director spoke too fast, was too jumpy and was disrespectful because he wore a baseball cap indoors.
About 16 minutes into this movie, Chandler is sitting outside an office as Fred MacMurray walks past. Chandler glances up at MacMurray from a paperback he is reading, a great clue of his identity.
The trivia items below may give away important plot points.
Director Billy Wilder originally filmed an ending where Keyes watches Walter Neff go to the gas chamber. It was seen only by preview audiences and was cut before the general release. The scenes contained the following actors (with their character names): George Anderson (Warden), Al Bridge (Execution Chamber Guard), Edward Hearn (Warden's Secretary), Boyd Irwin (First Doctor), George Melford (Second Doctor), William O'Leary (Chaplain) and Lee Shumway (Door Guard).
A different ending was shot, with Neff being caught by the police and executed while Keyes looks on in despair. Billy Wilder decided it would be poignant and fitting for both characters if instead Neff were to die in his office with Keyes by his side as he expressed his regret.
The part of Walter Neff was originally offered to George Raft. He insisted that he would only take on the role if his character turned out to be an FBI agent at the end, entrapping Barbara Stanwyck's character. As this ran completely counter to James M. Cain's original novel, he naturally didn't get the part.