Other mistake: In the very last scene of the movie, and just before Blondie shoots the rope that is holding Tuco on the grave's cross. You can see a car moving in the background, screen right of Tuco's head.
Continuity mistake: When the Batmobile is going to park (before the bomb scene) there is a sign saying "Mobey Dick Parking Only". When he is later carrying the bomb and passes by the Batmobile the sign is not there.
Factual error: John Wayne and James Caan are in the gunsmiths shop, and behind the gunsmith on the shelf are some products, one of these products is Bugler tobacco. Bugler tobacco was introduced in the United States in 1932. (01:00:00 - 01:02:00)
Visible crew/equipment: In the scene where Jeremy Kemp and George Peppard are playing daredevil in their planes and Kemp's plane hits a brick tower there is a shot of the plane plummeting to the ground. The alert viewer can see the shiny metal wires that were used to support and guide the plane on its way to the ground.
Revealing mistake: Near the end of the film when a building is collapsing and people are running to escape the falling debris, several women along with James Coburn are running up some stairs; a block of cement falls and hits actress Gina Golan right in the head. Instead of killing her on the spot, the bolder merely bounces off her head and she continues running up the stairs. (01:40:55)
Factual error: In the scene near the end of the film where Victor Buono is sitting in his chamber addressing his two captives, he opens a can labeled egg foo young with a can opener. He pours the liquid contents into a bowl. Egg foo young is an omelet and could not have passed through the small holes made with a can opener.
Deliberate mistake: When Raza is chasing the "empty" train, as it goes over the trestle just before he stops it, you can see the engineer in the train's engine.
Audio problem: During the chase at the end of the movie, the police cars' tires squeal in the dirt.
Visible crew/equipment: When Charles Hawtrey "jumps" onto the light near the end of the film you can see the strings pulling him across. The same can be seen with Jim Dale as well.
Factual error: Racer Dave Owens goes down to an unspecified Southern state to race and becomes a moonshine runner. However, the Dodge he drives in his illicit activities possesses California plates, as does the Plymouth driven by the IRS agents.
Revealing mistake: In this scene we see Frank Sinatra in a diving suit and helmet being lowered into the sea to look for a sunken submarine. As he is being lowered you can see the sun's reflection on the walls of a tank, meaning it was filmed in a large tank of water.
Visible crew/equipment: After Matt's arrested at the discotheque, when he's at the police station with Julian, the chalk actor's mark can be seen on the floor in front of Matt's feet.