Revealing mistake: When Phil kills himself by throwing himself off the roof, in the shot of him supposedly hitting the ground it is painfully obvious that it is a dummy. Not only does it hit the ground completely rigidly but the wig on it even noticeably flies off on impact.
Revealing mistake: During practically every scene with Dr. Nadir, the prosthetics to make his cranium look more 'alien' are visible. In particular, when the Queen realises he's been shooting down spaceships and not missiles and calls him a 'fool', at the back of the neck the line where the concealing make-up ends is evident. Throughout the rest of the movie the other Martians have similar if not even more obvious bald caps. (00:17:45)
Continuity mistake: When the prostitute is reflected in the mirror, her kimono bares one of the shoulders. She turns, and both shoulders are covered. (00:08:55)
Other mistake: In the opening credits, the composer of the movie score is credited as "Elizabeth Lutyens", with a Z. Her proper name was Elisabeth, with an S. (00:00:50)
Continuity mistake: During the second solitary visit that the Native Girl pays to doctor Bwana, she has to hold him steady after he drank the torpedo juice. Her right hand is in a completely different position in the various shots, and she lets Buster Keaton go once but is still holding him after the cut.
Continuity mistake: When the Pink Panther is sleeping on the bear-skin rug, the price tag reads "$350-00." When he rides in the rug, the two end zeros have disappeared, and in the shot after that, they are back again.
Factual error: Rifles and more so, cannons of the type shown in the movie were not close to being invented in the 1500s.