Plot hole: When George stops the machine for the first time, the candle burned down to about half of its size, which took according to his observations 98 minutes. But as the trip continues it takes seven hours for it to burn down completely. (00:25:45)
Factual error: When Janet Leigh is shown lying dead on the floor of the shower, there is a close-up of her open eye. The pupil is contracted to a pinpoint (obviously due to the bright lighting) where it should have been dilated. After the film was released, Hitchcock heard from several ophthalmologists who pointed this out and suggested he use belladonna eye drops in the eyes of "dead" people in future films, as the chemical prevents the pupils from contracting. (00:48:30)
Factual error: Here's a big historical mistake. The character of German Admiral Lütjens is depicted overall in this film as a wild-eyed Nazi fanatic. In real life, he was distinctly anti-Nazi, vehemently protested the anti-Semitic actions of Hitler's regime, and was himself subject to intense Nazi scrutiny as he was a quarter Jewish and his wife was half Jewish. He was one of many German naval officers who fought only for their country, not Hitler.
Continuity mistake: McQueen and Brynner take a hearse up the hill to deliver a coffin to the graveyard. When they go back down the hill, you can see a plume fall off one of the horses' heads, but in the next shot, the plume is back on. (00:16:05)
Factual error: When one of the men visits a doctor and learns he is terminal, the X-ray in the scene is upside down.
Continuity mistake: Before Pollyanna arrives on the train, when Jimmy Bean pushes the metal hoop down the road, two girls stop their doll carriages right beside each other and grab their dolls, but in the next shot their carriages are about 4 feet apart, which is now wide enough for Jimmy to run between. (00:01:10)
Revealing mistake: When the two dinosaurs are fighting besides the cliff, Malone and Jennifer Holmes hide behind a rock overlooking the cliff. One of the dinosaurs sweeps its tail, and knocks the two lovebirds over the cliff, but they fall onto a rock jutting out from the cliff. After we see them fall, there is a wide shot of the dinosaur swinging its tail. He swings it one way, then the other. After he swings it the first way, the tail freezes in mid-air for a split second, then swings the other way. It's obviously the same shot of the first tail swing, but played in reverse with a pause in between.
Continuity mistake: When the Jeep at the head of the army convoy starts off again, after being stopped at the temporary traffic lights set up by the crooks, the external shots show the Jeep passing the traffic lights. But the next shots from inside the Jeep show them passing the traffic lights a second time.
Visible crew/equipment: When the slaves roll the flaming ball down the hill, we see it strike several Roman soldiers. Look closely, they are actually stuntmen dressed in asbestos suits.
Revealing mistake: When Henderson and his wife are walking on the upper deck before jumping off, you can not see any of the superstructure above them that should be visible.
Factual error: In the scene where nickels fall on newspapers announcing that Roosevelt beat Hoover, at least one of them appears to be a Jefferson. The election occurred in 1932. The first Jefferson nickel was minted in 1938.
Continuity mistake: In the scene when Lulu Bains is prancing around in the dressing room, there is one steady shot of her. In this shot, as she moves around, the right strap on her outfit begins to slip off her shoulder. The shot ends by her side with the strap completely down her mid-bicep; however, in the very next shot, which is from the front, her right strap is back up, and it's her left strap which is halfway down. The print wasn't reversed to this effect, either.
Continuity mistake: When Sgt. Wilkins and P.C. Thurston go on patrol in the police car, it's registration number varies between scenes, from 892FPC to UUV133. (00:38:15 - 00:45:40)
Factual error: Throughout the movie, characters refer to the "Air Force", when in this time frame (1942-3) it was the "Air Corps".