Revealing mistake: After Forrester picks up the school bus sign, there's a shot of a Martian machine blasting at a bridge. Looking closely, the light poles can be seen through the machine, showing the model was matted over the background.
Revealing mistake: As the spaceship heads back into space, it leaves the same way that it crashed - they reversed the film. (01:18:30)
Revealing mistake: During the outdoor party at the Rainbow Cabins Marilyn asks the DJ to play "Kiss" in order to drive her husband George nuts, and after a couple of minutes he comes out and smashes the record. As he walks back to cabin B it's obvious this is a set as there's nothing inside the room except a blank wall. (00:20:15)