Deliberate mistake: Near the beginning, Col. Mortimer takes down a wanted poster and goes after the man. The man he kills looks nothing like the man pictured on the poster.
Suggested correction: There is a similar situation in the UK produced western movie "Carry On Cowboy" (released 1965). Johnny Finger/The Rumpo Kid (Sid James) shoots the sheriff of a US town. The sheriff is related to legendary sharpshooter Annie Oakley (Angela Douglas) and she swears revenge. Finding that Johnny Finger is staying in a saloon, Annie Oakley sets up a trap on the staircase. Another person (an uncredited extra) inadvertently walks up the staircase, so she shoots him instead. As he falls down the stairs she calls out "I'm terribly sorry I thought you were somebody else." Perhaps Col Mortimer has made a similar mistake. Being less polite than Annie Oakley he does not have the good manners to apologise.
Suggested correction: Is that a mistake? (Either on the part of the people who made the film, or assuming this was real life, on the part of Colonel Mortimer?) They're a pretty bloodthirsty lot in this film, and nobody seems to really care who gets shot. Maybe he figures he can get a bounty for that person anyway.
Deliberate mistake: When Ringo sprays his assassin with orange juice, it doesn't reach as far as the sofa. But it still splashes over the inch-high Paul. Even if it had flown that far, Paul is on the far side of the sofa and the angle is impossible.
Deliberate mistake: In the scene inside General Kohler's command center when Kohler is giving Colonel Hessler a tour of the war room he points out to Hessler a clock on the wall whose increments represent 1 hour and that the attack has to be over within so many hours. Later in the movie, just when the attack starts, this dormant clock's hand immediately springs forward and ticks through 2 increments, thus representing 2 hours passing in 2 seconds.
Deliberate mistake: The theatre is said to have been closed down "years ago". But all the theater props are still there, and the place shows no sign of disuse, it is not even dusty anywhere. The electricity and water are also still hooked up and functioning.
Deliberate mistake: When The Kid visits the farm, the red truck in the background is a Fleetside truck that is definitely not from the 1930s.