Revealing mistake: When Leslie is fighting the soldiers, one soldier hits a second soldier with his rifle. The rifle can be seen to bend around the soldier's body and then straighten again. (02:12:10)
Revealing mistake: When the gang tries the growth formula in the theatre, they quickly grow out of all their clothes until they are naked. But the scrunchy in Jean's pony tail is still in place and shows no signs of being stretched, even if the pony tail now is 20 times bigger.
Revealing mistake: When the tail breaks off of the "German" machine and it careens around the field, you can see the little steerable tail wheel used to control the plane in those scenes. In all other scenes this plane has a tail skid.
Revealing mistake: Stan's car gets a flat from the severed Eye Creature's hand puncturing the tire. The scene shows the hand going for the tire and when it grabs it, the rubber fingers bend in and some bend sideways.
Revealing mistake: In the scene at the end of the movie where Lee Marvin is running interference during the escape by shooting in the air, horses pulling a beer wagon get startled and run into the street where the wagon turns over. At the beginning of the shot, when the horses begin to bolt, you can see the stuntman driving the wagon. He is sitting low behind the wooden front of the wagon (which has holes cut in it so he can see out).
Revealing mistake: When Charlie Brown stops to watch Snoopy sitting atop the doghouse, eating dog bones, the pile of bones never goes down even though Snoopy takes from the pile three times. (00:03:25)
Revealing mistake: Near the beginning of the film, when Clang is outside the Beatles' flat on his delivery bike, you can plainly see the rope tied to the front of it giving him a pull as he starts to ride off. In the next shot the rope is gone.