Continuity mistake: When Pnub's head is picked off the kitchen table at the end of the hand-cutting scene, the ring of blood that formed around Pnub's neck stump is joined with the larger pool of blood that it came from. When Pnub and Mick come back to the kitchen later on, the ring is no longer attached to the larger pool. Blood does not evaporate like that when it dries.
Continuity mistake: The cheesy puffs that are thrown to the decapitated head in the chair change from scene to scene.
Continuity mistake: When Anton is going to the dance and is backing out of the driveway in the pickup truck, you can see both of his hands on the wheel. This is after he has cut his hand off.
Continuity mistake: At the very beginning of the film, Anton's mom and dad are lying in bed together talking. Right after Anton's dad explains to his mom how "Anton never even helped me with the Halloween decorations", he turns the light out and lies there with both of his hands behind his head. A split second later, Anton's mom looks up at the ceiling and sees the words "I'm underneath the bed" glowing on the ceiling and begins screaming. The camera pans back to Anton's dad, and both of his arms are at his side.