Continuity mistake: When Waldman is telling his wife Alice how disgusting her dog is, the way he holds his spoon keeps changing between cuts.
Continuity mistake: When Geena Davis stabs a man in the eye with a syringe, in one shot there's no blood on his eye, but in the very next shot there is.
Continuity mistake: After Timothy has kidnapped Caitlin from the church, it cuts to an exterior wideshot of the car heading to Niagara Falls and we can see the rear-view mirror on the windshield, but in the closeup of Charly and Mitch the mirror has vanished.
Continuity mistake: In the scene where Charlie forces the truck driver out of the semi, right after she points her gun at him, the shot cuts to outside the truck and it looks like the driver fell out the driver's side door. This does not make sense as Charlie was blocking that door.
Continuity mistake: In the scene where Charlie forces the truck driver out of the semi, just as he hits the ground you can see the door of the truck closing. Then when the shot cuts back to Charlie the door is seen closing again.
Answer: A 1966 Ford Galaxie-500 XL. There's a website that lists the vehicles used in the movie.