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.
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: 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)
Continuity mistake: When Bugs is performing his shooting stunt in the saloon, you can see the entrance behind Sam has nothing between it. When Sam tells Bugs he's missed, we cut to Bugs who says "Wait!" and then return to Sam, and this time there are doors between the entrance.
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 Mama Ape takes Bugs Bunny out of his bed, Bugs is wearing a baby hat, but when Mama is holding him in the next shot, the hat has disappeared.
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.
Continuity mistake: When Sylvester runs into the yard after throwing the smoke bomb into it, the door of the yard is shut but in the next shot it is open.
Factual error: Karnak was an Egyptian city, not one of their gods.
Continuity mistake: When Ben reiterates "We're going to Dry Fork", Randolph Scott's hands are joined on the reins. Shot from behind, you can see by the arm position that they are apart. (00:20:45)
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)
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)
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: When Elvis hands a pair of binoculars to his pappy, you can see there is a swarm of flies buzzing around Pappy, but in the next shot the flies have disappeared.
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.