Continuity mistake: When Roy leans towards the steering wheel to watch the UFO, the position of his hands over the wheel changes between shots.
Continuity mistake: The mashed potato that Roy serves himself swaps from stiff to creamy between one shot and the other.
Chosen answer: I own the original (not special edition) DVD and I can always freeze the film and point out to people where the alien is and they see it too, but I can never see it when it's on TV or on my friends VHS copy, maybe it's just a 'gift' for the DVD owners?