The Queen Mary appears in the background in the scene where Mitty takes a taxi to Pier 47 in an effort to retrieve his briefcase. This liner, used as a troop transport during World War II, is still painted in its wartime gray in this scene, filmed about a year after the end of the War.
Author James Thurber acknowledged that the character Walter Mitty was based on his friend, writer Robert Benchley. Thurber said that he got the idea for Mitty from the character created by Benchley in a series of shorts that he made for Fox and MGM, respectively, in the 1920s and 1930s. Thurber is also on record as saying that he hated this film and that Danny Kaye's interpretation of Mitty is nothing at all like he intended the character to be.
In an unused Mitty dream sequence, Boris Karloff appears as the Frankenstein (1931) monster, which explains Mitty's fear of Karloff's character. Test photos of Karloff in makeup (by Jack P. Pierce) exist, as well as a letter from Universal Pictures to Samuel Goldwyn Pictures giving permission to use the makeup design.