Revealing mistake: When the killer is dragging the girl's body with the meat hook, you can easily see that it is a doll. (01:18:45)
Revealing mistake: When Julie is in the room filled with ice, some of it jiggles when she moves it, probably a prop made of jelly.
Continuity mistake: After Barry has jumped into the water reclaim the crown, he comes out of the water with a perfectly clean shirt, but in the next shot the blood is back on his shirt as expected. (00:22:50)
Officer David Caporizo: Oh, and did this killer use his hook to cut all your hair off?
Helen: No, he used scissors, asshole.