Continuity mistake: When everyone is running out of the theater, a woman with a red belt and yellow purse can be seen exiting with the other terrified patrons. A few seconds later, the exact same woman is seen running out of the theater again.
Factual error: In the final scene there is a shot which shows a Land Rover in the distance. Land Rovers were not built until after World War 2.
Revealing mistake: When McKay and Ramon are riding into Blanco Canyon to rescue Julie, you can see a diesel loading shovel with its bucket raised in the bottom of the frame of one of the scenic shots. Presumably the scene was shot in a quarry and they didn't get all the equipment out.
Factual error: The film was released in 1958 but depicts a 1943 World War II mission in the Pacific by a US submarine capatain played by Clark Gable and his first officer played by Burt Lancaster. In two separate scenes the crew listens to a "Tokyo Rose" broadcast on radio and the background music is "Kiss Me Once, Kiss Me Twice, It's Been a Long Long Time" by Sammy Cahn and Jule Styne. The song was not released until September 1945, one month AFTER the end of the war in the Pacific in August 1945. The song was famous for celebrating returning troops and therefore also makes no sense in the context of 1943.
Other mistake: In the opening scene on the airplane, one of the men tells Lt. Cable, "The captain wants to know if you'd like to sit up in the cockpit with him?" Buzz Adams, the "captain" referenced in this line, is only a lieutenant. Admittedly, "captain" is a standard aviation term for the pilot of an aircraft, but it would be unlikely to be used in this situation, since the term has a specific military meaning.
Factual error: The Vikings raided England in the 9th and 10th centuries. The first castles were not built until post 1066. The castle in the film has rounded towers, crenellations and machicolations, which would date it at approximately 1300. That would tend to suggest that these Vikings were 400 or 500 years old, or that they had access to a time machine.
Continuity mistake: After Maggie (Liz Taylor) goes outside to confront Brick at the car during a raging rainstorm getting thoroughly soaked, she appears a short time later in the drawing room in the same dress, immaculate hairstyle and makeup, looking like she hadn't seen a single drop of water. (01:11:00)
Other mistake: After Van Helsing realises Dracula's coffin is in the cellar of Michael Gough's house, he hears a scream and runs to find the housekeeper Gerda overwrought and hysterical. He needs to find out where Dracula has just gone, and so he gives her a slap. It's hilarious how loud the sound of this is.
Continuity mistake: In order to tiptoe across the tacks without being hurt, Tom puts a metal gauntlet on his feet. At this point, you can see the floor is completely covered in tacks, but when Jerry and Nibbles are at the same spot a little later on, the tacks have disappeared.
Continuity mistake: When Will Stockdale is at the Purple Grotto, at one point the cup full of liquor is at different levels.
Visible crew/equipment: When the aliens blast off at the end of the film, the bright light causes the shadows of the actors and vehicles, etc, to appear on the painted backdrop of desert and sky.
Factual error: When the ship is being launched a champagne bottle is smashed against the hull. Harland & Wolff, like many shipbuilders, did not smash champagne bottles against the hull.
Continuity mistake: The interior of the ship is quite spacious, a central atrium on each level, with crew quarters and storage spaces opening off it. Yet, when the two officers take a space-walk down the length of the ship, it appears to have a diameter of less than 20 feet.
Factual error: As the stagecoach rolls into Prescott, Arizona, the road winds among hundreds of Saguaro cacti. Prescott is far beyond the northern limits of the Saguaro.
Visible crew/equipment: When Isabel Jeans is telephoned by Madame Alvarez and told that Gigi has refused Gaston's advances, she gets out of bed and walks across the bedroom. As she passes a cheval (full length) mirror a pair of retreating jean-clad legs and a hand feeding out cable can be seen in the reflection.
Revealing mistake: When Corporal Bin's group of men eventually arrive at Dunkirk, they speak to a soldier adding sandbags to a Vicker's gun position. Here (and later on in the film when it is shown firing) it has a blank-firing adaptor prominently fitted to the front. Additionally the belt of ammunition shown going through it is filled with blanks - no bullets project outside the other side to that of the actual cartridge cases.