Revealing mistake: In a scene where the canoes are shooting the rapids through a sheer cliff you can clearly see a stuntman climbing out of the water onto the rock.
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: After Alice falls down the hole, into the leaves, she gets up and runs down a stone to follow the White Rabbit. As she runs down the stone, it quite visibly squashes down under he feet, revealing that it is foam.
Revealing mistake: Freeman Lowell has several cargo containers dumped off the spaceship, to make it appear the ship has suffered an accident. A wide shot shows the ship receding in the distance, with the containers rolling weightlessly in the foreground. As the foreground containers pass slightly in front of the more distant ones, they don't mask them; their images overlap. The containers were apparently composited into the shot with simple multiple exposures. (00:35:40)
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: When the sword mistresses kill the ninja we see them slice his whole nose off, however when the ninja's dead body is rolling across the floor you can see his nose is still attached. (00:15:32)
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 Anguirus makes his sacrificial charge against Gigan, the hand that is moving the Anguirus costume can be seen holding it.