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 Stewart's wrestling with the alligator look closely and you can see the black strap keeping its jaw shut.
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.
Revealing mistake: At the end of the film, in the extreme close-up shot of the Dual Flintlock pistol Ronin having his forehead hacked by Itto's sword you can see his hair is a wig. (01:20:27)