The production license required that any evidence that the Wawona Hotel within Yosemite National Park was ever used to impersonate an Allied Military Hospital in postwar Bavaria had to be totally removed within 24 hours after the movie's exodus. Compliance with this condition was the only way Producer William Perlberg could get into the National Park area for his picture.
The fake 1950 newspapers given to Major Pike depict "President Wallace." Henry Wallace was Vice President of the United States in 1944, when the film actually takes place. He was not included on the Democratic presidential ticket later that year and was succeeded as Vice President by Harry S. Truman.
The writing credits not only claim Roald Dahl's short story, "Beware Of The Dog", as the source of the plot but also an original film story by Luis H. Vance and Carl K. Hittleman. It has been suggested that MGM bought the Vance-Hittleman plot whilst unaware of the Dahl story, also unknown to the writers and director George Seaton. However, when the script was coincidentally offered to Dahl's wife, Patricia Neal, she spotted the resemblance straight away and brought it to her husband's attention. (She turned down the female lead, which went to Eva Marie Saint.) MGM was required to pay a large sum for the film rights of Dahl's very brief story to avoid a lawsuit.
This movie features both Sig Ruman who played German internment camp guard Sergeant Schultz in Stalag 17 (1953) and John Banner who played one by the same name in Hogan's Heroes (1965). Coincidentally, Ruman's only scene is with Banner.
James Garner looking out of the window to see the fake "camp" is exactly the same scene as Patrick McGoohan in the opening of TV series The Prisoner, and there are many similarities in plot. Particularly the Prisoner episode Schizoid Man has the same plot swerve with No 6's fingernail mark giving the game away the same as James Garners finger paper cut here. McGoohan must have seen this movie as an inspiration for the idea behind The Prisoner.
James Doohan: The soon-to-be "Montgomery Scott" of Star Trek (1966) is uncredited as a British orderly in the opening scenes. Doohan served in Canadian forces during the Normandy Invasion (which the film is about) where he lost part of a finger. Future Imperfect (1990) and Stratagem (2004) were inspired by this film.