Factual error: In the scene near the end of the film where Victor Buono is sitting in his chamber addressing his two captives, he opens a can labeled egg foo young with a can opener. He pours the liquid contents into a bowl. Egg foo young is an omelet and could not have passed through the small holes made with a can opener.
Revealing mistake: At the end of the car chase when the two cars collide, the cliff shown to the right is a painting added to the scene to suggest a sharp drop off.
Continuity mistake: When Gail tries to flee the wagon during the storm, the back of the car looks brand new; this despite being repeatedly rear-ended during the car chase.