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)
Revealing mistake: During the chariot race, where the contestants are riding towards the screen, tyre tracks from the camera vehicle are clearly visible imprinted in the sand. (00:20:50)
Revealing mistake: In the scene where the soldier has to have his leg amputated, when a soldier steps over him, he accidentally hits the knife, which bends, revealing it's a rubber prop.
Revealing mistake: A boulder tumbles towards James Mason and his party though a cave. With all the smashing against the walls and floor of the cave, the boulder stays entirely intact. However, just before the boulder hits a wall with two tunnels while flying through the air, the boulder now shows two majors fractures that were unseen earlier. The fractures were added to the boulder to give it a more dramatic impact by it breaking up with one piece nearly striking James Mason. (00:55:50)
Revealing mistake: Watch the back projection of the Great Northern desert in the train carriage windows. At one point a lorry appears, waiting at a level crossing for the train (that the film was shot from) to pass.
Revealing mistake: A driver pulls out into oncoming traffic and hits another car, It is obvious that when the scene was filmed, the driver stopped just short of the other vehicle. The sound effect of a collision is dubbed in and the front of the two vehicles is never shown.
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.
Revealing mistake: When Wilby is in the car being chased by the police officers while he is a dog, in some scenes the dog is a real dog and in other scenes it is just a person in a dog costume.