Revealing mistake: When the UFO makes the huge flash that knocks everyone in the cemetery down, one of the police officers kicks a tombstone as he falls and it wobbles back and forth. (00:13:35)
Other mistake: When the Behemoth swims up the river & capsizes the ferry, a static model is used that bears no resemblance to the animation model seen throughout the film.
Revealing mistake: Near the beginning, when police Lieutenant Rowan is inquiring on the death of Ken Drake, there are only 4 men in the room, all facing one another in a wide shot. The camera cuts to a close-up of Dr. Bradford for a couple of seconds, and there is a distinct puff of cigarette smoke passing behind him, but none of the characters in this scene are smoking. Lieutenant Rowan does smoke later in the film (in fact, he's the only character who smokes), but he's not smoking in this early scene. Apparently, the close-up of Dr. Bradford was borrowed from omitted footage in which Lieutenant Rowan was smoking.Charles Austin Miller