Revealing mistake: When the guys are driving down the road, you can see Michael isn't under the truck. Yet 2 minutes later, he climbs in the bed. (01:16:25 - 01:18:10)
Revealing mistake: When Michael sticks his thumb in the ambulance guy's head, you can see the inside of the fake hand.
Revealing mistake: Dr. Loomis fills his tank, and when the camera changes it is not Donald Pleasance. (00:18:30)