Revealing mistake: Rock Hudson angrily picks up Doris Day from her bed, blanket and all, and carries her through town to his apartment. When he is walking down the sidewalk, the blanket slips and the supporting wooden board underneath Doris Day is visible. This made carrying her easier.
Continuity mistake: The background shots of the Matterhorn show it with a clear sky, then a cloud around it, then a clear sky again. This keeps happening.
Continuity mistake: After Sir Hugo has stabbed the girl on the moor, no blood is visible on the knife he used, however after he drops it (because he is attacked by a hound) blood has now appeared on it.
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.
Continuity mistake: When Molly (Sandra Dee) grabs the letters she had hidden in the suitcase under the bed, her dress is still unzipped in the back. After ranting at her mother for having read the letters, she throws them into the fireplace, only now her dress is completely zipped up.
Continuity mistake: In the start of the movie Charles says that he has got a letter from his aunt in Italy. But she lives in Brazil, and you don't hear anything about his aunt being on vacation to Italy.
Continuity mistake: When Richard Hannay jumps from the Sheriff's window into a passing truck it is full of bales of hay. The next time we see him in the truck it is full of sheep and the bales of hay have vanished.
Continuity mistake: The doctor just killed Mr. Fleming. Cut to Agnes Moorehead playing cards; She is casting no shadow on the desk from the side view, but in the view with the camera in front of her, she is projecting a shadow. (00:11:35)
Factual error: The movie takes place "somewhere in the South Pacific, 1942", yet the transport plane taking LTJG Braden to Hawaii has post-war markings.
Continuity mistake: Sam Boone walks Ben Brigade to the horses holding his rifle, and they have a bit of a chat by and about the captive Billy. During this scene, the handkerchief at Randolph Scott's neck waves like mad in the wind over his shoulder under one camera angle, and it is still and in front of the chest in the other. (00:09:30)
Continuity mistake: When Stanley is shown around the cake factory he takes his hat off and puts it on a conveyor belt and it is carried into a machine and covered in icing. But in the scene before this with the supervisor saying "and this is the enrobing chamber" you can see his hat come into shot on the conveyor belt already. In the next shot he still has his hat on and only then takes it off and puts it onto the conveyor belt. (00:13:08)
Other mistake: After the intro, one girl in the bar peeks from the window and goes; "Say, here comes Gordy and Jennie." And indeed the duo is getting off the car and joins them. The problem is, the window is on the opposite side of the entrance and there's diegetic music playing throughout the scene. In other words, she saw them parking to the left, but in a split second they are coming through a door on the right. (00:02:40)
Continuity mistake: Christopher Lee looks outside his useless nephew's room and spots two hot Swedish girls. Renato Rascel has a bottle of wine in hand and walks towards him, but the bottle is gone when he tries to stop him. (00:23:40)
Continuity mistake: The car is out of gas, and Sylva Koscina gets impatient. As the shot changes, Walter Chiari's arm is on top of the car door (it wasn't in the first shot) and Dorian Gray crosses again her arms on top of the bag - assuming the same pose she already had. (00:17:00)
Revealing mistake: When Holmes kills the guineapig-human hybrid, the entire scene is ridiculous. In the first shot, the guineapig has tiny human hands that look to be about a half-inch at most. Holmes then steps on it, and in that shot it appears to be a different type of rodent entirely. Then we see the human hands under his shoe flexing in pain, and they look to be significantly bigger than before based on the scale of his shoe... at least 5X bigger than they were.
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.
Deliberate mistake: For all exterior shots on the surface of Mars, the crew's "pressurized" space helmets have no face-plates (their faces are fully exposed to the hostile Martian environment). The transparent face-plates they intended to use reflected far too much studio set lighting, such that the glare would have obscured the actors' faces. On a $200,000 budget and a 10-day production deadline, they simply scrapped the face-plates and shot the scenes with wide-open helmets.
Continuity mistake: When the judge gives Woody his money after he won the championship play-off, the notes on the top of the two left piles have nothing written on them, but when we see a close-up of Woody in the next shot, dollar symbols have appeared.
Continuity mistake: Susie, a six-year-old girl, leans over a bathtub and reaches for a rubber duck. She falls into the tub but it obvious the tub has no water. (The actress, Terry Burnham, landed on a pad or cushion.) Immediately after she falls, there is a very noticeable jump in the film. Then water splashes up but the splash is much too high to have been made by the little girl. The next scene shows the mother entering the bathroom and the little girl, now completely drenched, standing up in the bathtub.
Other mistake: A police officer fires two shots, hitting a bank robber in the back. The "bullets" do not make holes in the robber's coat. All they do is create two tiny puffs of dust.