Trivia: Unknown at the time, two future Star Trek references are made in this film. The director, Robert Wise, would go on to direct Star Trek: The Motion Picture, and at the end of the film when discussing the cloud seeding, a caption on the video monitor reads out "Nimbus 3". This was the name of the planet on which Sybok takes prisoners in Star Trek V: The Final Frontier.
Trivia: Christopher Lee's only western.
Trivia: This film marked the directorial debut of Clint Eastwood.