Revealing mistake: When the blonde stripper slaps the brunette slapper, for calling her "leftovers," in the closeup of the brunette being slapped, the hand is that of a male; very rough and hairy, and not the blonde stripper's.
Revealing mistake: After Kurt has had his arm torn off by the monster in the closet, in various following scenes the bulge of the arm being hidden underneath Kurt's jacket is very blatant.