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)