Continuity mistake: When Ray first arrives at Devil's Tower and stops the station wagon, the broken fence post resting on the hood changes positions between shots. In the view of him through the wind shield, the post is lying straight, parallel to the length of the wagon. In the next shot, it is suddenly at an angle, even though the car hasn't moved. (01:21:30)
Continuity mistake: The mess next to the fridge differs between shots, the egg box flips over for example.
Continuity mistake: When Ronnie rescues Roy from the bathtub, a rope next to him disappears between one frame and the other.
Continuity mistake: When Roy is driving to Devil's Tower he is about to crash against two cars. From the opposite angle the cars are different.
Continuity mistake: In India, Claude asks the Guru where the sounds came from, while a huge crowd walks along the desert. When a man in blue addresses the crowd to ask them, the crowd on the right side is gone, and the ones on the left aren't walking but standing perfectly formed like an army.
Continuity mistake: In Jillian's house, when the aliens launch the floor vent it lies on the right side, half a meter away from the hole. A frame later it's lying skewed on the hole. Should the aliens have moved it, a sound would've been heard.
Continuity mistake: When Roy says to Ronnie, "I saw something last night that I can't explain.," and he bridges his arms across the door frame his forearms are parallel to the ground. In the following shot, when Ronnie straightens up, Roy's forearm points upward. (00:36:15)
Continuity mistake: When Roy is shoveling dirt through the window he leaves his shovel on the wheelbarrow. When he comes back three seconds later, the shovel is in a different position.
Continuity mistake: When Roy starts throwing plants in the window, the glass gets smashed. Then they open it. When Roy closes the window after he climbs in, it is no longer smashed.
Continuity mistake: Roy's first encounter is with a ship that comes up behind, goes overhead and briefly reappears in front. When it's glimpsed passing above, it's moving towards him as if it came from ahead.
Continuity mistake: After Roy fills their kitchen with shrubs, bricks, soil, and chicken wire, Ronnie takes their three kids out of the house and into their station wagon. She tells her kids to lock the doors, but the driver's side door lock is up (unlocked). When Roy walks around the driver's side to speak with Ronnie, the driver's side door lock is now down (locked). (01:10:05)
Continuity mistake: Barry is leaving his house, going towards the trees. Jillian looks out her upstairs window and Barry as well as the immediate area surrounding him are drenched in bright direct light, as if from a spotlight mounted on the side of the house. However, from an outside angle of the scene he is not bathed in light, and neither is the area he is in.
Continuity mistake: The pattern of shaving cream on Roy's face changes during the scene in which he gets fired.
Continuity mistake: When Barry is taken from the house, just before that happens we see a grate get blown out of the floor and it lands on its side. In the next scene the grate is back in the hole, but at an impossible angle, even if it fell in.
Continuity mistake: When Richard Dreyfuss is building the model of the Devil's Tower in his living room, behind him in the sliding glass doors you can see that it is raining, and when he turns around and walks to the door to look out, it is now sunny, and people are out side mowing the grass and children playing. (01:15:40)
Continuity mistake: Roy is about to run Barry over with his truck and stops on the side of the road. The position of the papers on the dashboard changes between shots.
Continuity mistake: Ronnie says "It's one of those things" and Roy follows her with his hand filled with shaving foam. In the next angle the amount of foam on the right hand is bigger.
Continuity mistake: When Barry walks outside the house and his mother calls him, from the shots inside she is surrounded by curtains moved by strong air. From the opposite angle the curtains are gone.
Continuity mistake: The mashed potato that Roy serves himself swaps from stiff to creamy between one shot and the other.
Continuity mistake: When Jillian's kitchen goes wild, the heater's lids fly off and reveal some red foam which ends up breaking and making a hole. A frame later from a new angle the foam is fixed.
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?