Continuity mistake: When they are putting Harry on top of the car his feet are pointing up, but when they are driving down the road Harry is now face down on top of the car.
George Henderson: We've got some big guns and some big-big guns but I'm afraid I'm all out of big-big ammo.
Sarah Henderson: Where's the roast?
George Henderson: I'll go get it.
Nancy Henderson: The roast is resting in a shallow unmarked grave in the backyard.
George Henderson: Oh. Well, there's plenty of other stuff.
Dr. Wallace Wrightwood: Are you vegetarians?
George Henderson: Sometimes. It depends on the guest.