When Carol arrives at the doctor's house, the garage door is up. Minutes later, when Alex leaves in the hat and trenchcoat through the front door, the garage door is closed.
Jack Donner was erroneously listed as Jack Doner in the opening credits.
When the monster turns the light on in the beachfront house, instead of turning the handle on the lamp, it turns on by his touch. Those lamps turned on and off by turning the handle clockwise.