Revealing mistake: When Louis is trying to get Gage off him near the end of the movie, as he's struggling in a few shots you can plainly see it's not really Gage but a dummy made to look like him. Looks like a doll. (01:33:35)
Revealing mistake: In one shot when Alice is in the shower, as she turns for the soap you can tell she is wearing brown underwear. (00:03:30)