The car Doug drives from the prom to the radio station changes three times over six minutes.
When Joe comes to pick up Katie in the Flying Saucer Truck, you see him shift down 3 notches which is in to drive, but you see the truck backing up not moving forward.
Over the course of a minute, it goes from having no tree limbs against the front porch to the tree falling down and there being a huge tree limb against the front porch.
When Richard is in the kitchen talking to Doug, he speculates about what would happen if Katie met a duke or a prince in Europe. He asks "What about that Prince Charles guy?", and Doug responds, "Prince Charles is married." However, both men's lips form the word "Andrew" instead of "Charles."