Visible crew/equipment: As the villagers are running away from Kong, when the mother rescues the young child, in the next shot look to the back right side of the screen. A member of this movie's production crew steps into the shot, stands there watching as the movie extras are running, and the shot cuts away. (01:17:29)
Revealing mistake: When the woman at the bar brings Jack the mustard which she forgot, Jack puts his napkin in front of his mouth. A fraction of a second before that, you can see the down-side of his face which should be invisible. Instead of nothingness you see it's all black. That is material used for the special effects, but they didn't 'make it invisible'. (00:06:50)
Continuity mistake: Igor's face is not disfigured on New Year's eve 1933, when he looks out at the crowd. The next scene in the morgue he is disfigured.
Revealing mistake: When Denham is rowing the boat to the island - an obvious rear projection - the oars never touch the water.