Continuity mistake: When Mac's on the windshield and the car starts to dodge cars, one shot from inside the car shows the alien has disappeared.
Revealing mistake: In the pile up scene, due to MAC covering up a man's windshield, a huge truck swerves and flies over a car, only the big black ramp used for the stunt is rather visible. (00:11:00)
Continuity mistake: During the dance at McDonalds tables and chairs suddenly disappear from the place and are replaced by dancers.
Continuity mistake: When Mac's on the windshield and the car is dodging traffic, the co-pilot kid appears and disappears.
Revealing mistake: In McDonald's when Mac stretches his arm, notice that it's separated several inches from his body and much thicker, and is really a big sleeve coming form under Eric's armpit. In fact, you can see Mac's real arm next to his body, hanging down.