Revealing mistake: When McDonald is in the tunnels and is called to pick up the phone, he picks up a red phone. It is a standard Bell TouchTone desk phone. To make the phone look more futuristic, there was no cord and it was disguised as a cordless phone. The port that the cord would plug into is covered by a piece of colored tape. This also can be seen in the operations center of Ape Control when the worker picks up the phone.
Revealing mistake: When the ship is upside-down and they're trying to get Susan down from the table, you can see that the table really isn't attached to the ceiling. You can see the center pool split into legs that are supposed to be connected to the floor, but when Susan moves around and shakes the table, the legs shake and you can see space between them and the floor. Even if the other legs outside of the shot were connected, the table would be leaning under Susan's weight.
Revealing mistake: When Itto is bathing, near the beginning of the film, he hears the clanking sound and then there is a close-up shot of his face. The start of his wig, the hairline, is visible. (00:08:48)
Revealing mistake: During the flashback sequence when Gunbei's double is decapitated, his severed head hits the floor but you can see that the actor's head is still inside his clothing. His top has been pulled over his head to make it look like his head has been cut off. It's even more obvious in the wider shot right after. (00:27:42)
Revealing mistake: During the iconic dojo brawl scene, Bruce Lee at one point picks up two men and whirls them around. It's obvious in the wide shot that they are just dummies.
Revealing mistake: At one point when the soldiers are walking through the jungle, one of them steps into a trap and is pulled up into the trees to be killed by Indians. However, if you watch this scene carefully, when the soldier (who steps into the trap) walks into frame you can see a wire already attached to his foot leading up into the trees. He doesn't step into a trap. (00:22:26)
Revealing mistake: When Shaft fights the bad guys disguised as flower delivery men, both die with their blood packs that explode triggered by visible pyrotechnics - kinda odd to shoot a guy and see literally flames burst out from his chest or back before any blood comes out. (00:48:50)
Revealing mistake: When Itto puts the cover on the baby carriage it's obvious that the sudden downpour of rain is just a sprinkler placed in front of the camera. Pay attention to the cover, Itto's clothing and the puddle behind the carriage, they remain completely dry/untouched. (00:11:00)
Revealing mistake: The protagonist jumps from a bridge and boards the train to try to save the Professor. When he is walking on the top of the carriages, look at the treetops in the background; the train is stationary. (00:12:00)
Revealing mistake: At the beginning, when the woman in the flotation seat is paddling backwards, you can see a fishing line attached to the back of seat that is being pulled to help her move backwards.
Revealing mistake: When Anguirus makes his sacrificial charge against Gigan, the hand that is moving the Anguirus costume can be seen holding it.