Visible crew/equipment: While the winding road up the "bump" is being built, Ram is on the radio updating on the Legion's movements, and he says, "They're moving up hill 49, half a mile from our road." At the very start of the next shot when it cuts to Magda, Marcus, and Asher at the jeep, we can see the film crew's clapperboard in front of Kirk Douglas, as it swiftly moves offscreen at the bottom right side of screen. (02:04:10)
Plot hole: Even if the white blood cells will attack and destroy the sub and the body of Doctor Michaels the atoms would still remain and take normal size after the critical 1 hour is up. This would also apply to the laser gun which they forgot or left behind on purpose, as well as several dozen litres of saline solution which were miniaturised and pumped into Benes' body. He's in a lot of trouble.
Other mistake: In the very last scene of the movie, and just before Blondie shoots the rope that is holding Tuco on the grave's cross. You can see a car moving in the background, screen right of Tuco's head. (02:55:29)
Suggested correction: I've just watched this scene; there's no car visible. There's a bit where Blondie prepares his gun prior to aiming, then the camera switches back to Tuco. To the right of Tuco, in the background, a blurry something can be seen for maybe a second moving right to left. The object is far too blurry to identify. There's no reason to believe it's a car. It makes more sense that it's a horse-drawn wagon.
Continuity mistake: When the Batmobile is going to park (before the bomb scene) there is a sign saying "Mobey Dick Parking Only". When he is later carrying the bomb and passes by the Batmobile the sign is not there.
Factual error: John Wayne and James Caan are in the gunsmiths shop, and behind the gunsmith on the shelf are some products, one of these products is Bugler tobacco. Bugler tobacco was introduced in the United States in 1932. (01:00:00 - 01:02:00)
Visible crew/equipment: In the scene where Jeremy Kemp and George Peppard are playing daredevil in their planes and Kemp's plane hits a brick tower there is a shot of the plane plummeting to the ground. The alert viewer can see the shiny metal wires that were used to support and guide the plane on its way to the ground.
Revealing mistake: Near the end of the film when a building is collapsing and people are running to escape the falling debris, several women along with James Coburn are running up some stairs; a block of cement falls and hits actress Gina Golan right in the head. Instead of killing her on the spot, the bolder merely bounces off her head and she continues running up the stairs. (01:40:55)
Revealing mistake: Although "Man" is supposed to be completely naked, there are several shots where his flesh-colored briefs are visible. Most noticeable when he is initially set loose to be chased.
Visible crew/equipment: When Charles Hawtrey "jumps" onto the light near the end of the film you can see the strings pulling him across. The same can be seen with Jim Dale as well.
Audio problem: During the chase at the end of the movie, the police cars' tires squeal in the dirt.
Continuity mistake: Throughout the movie Elsa wears a collar. In the scene where she runs away the collar is visibly in place - a few minutes later, when she's found with the elephant, the collar has disappeared.
Continuity mistake: When the dinosaur charges toward Tumok, and Tumok lies down to shove the spear into the creature as it runs upon him, the dinosaur looks several times bigger than it did in all the previous scenes.
Revealing mistake: In this scene we see Frank Sinatra in a diving suit and helmet being lowered into the sea to look for a sunken submarine. As he is being lowered you can see the sun's reflection on the walls of a tank, meaning it was filmed in a large tank of water.
Visible crew/equipment: After Matt's arrested at the discotheque, when he's at the police station with Julian, the chalk actor's mark can be seen on the floor in front of Matt's feet.
Continuity mistake: When the four kids uncouple the coach from the engine Carole is wearing trousers. The stationmaster tells them to stand clear as the engine pulls away, in the first shot of the children after the engine has gone Carole is still wearing her trousers but in the second shot Carole is now wearing a skirt.
Other mistake: Fred's tie gets unraveled when he and Barney are trying to escape the Green Goose's dungeon. Yet, his tie is fixed a few minutes later.