Revealing mistake: When Harry and Samantha are shot at in the elevator you can see a number of the dark marbles that were used for the effect rolling on the floor.
Revealing mistake: When Dolph goes into the bar near the beginning, he headbutts a bald guy. You can see that he doesn't even come close to making contact. Still, the guy has a broken nose.
Revealing mistake: Clearly not Susan Blakely when she goes topless. Her hair suddenly becomes curlier, that's a body double.
Revealing mistake: When Jemma enters the headshrinker's laboratory, there is a table with three heads on it each encased in glass. When it goes in close-up on the middle head, you can see that the table has a hole where the actor can slip in his head.
Revealing mistake: During the fight montage, the winner of the first match wins by kicking his opponent in the face. His foot never makes contact.