Revealing mistake: In all the scenes where Tum Tum kicks the ninjas, you can tell it is a fake leg in the closeups.
Revealing mistake: During the scene in which the small group of GIs, led by the young go-getter officer played by John Cusack, attack the Japanese hilltop bunkers, they seemed to be equipped with magic bullets. The American soldiers are firing wildly in all directions but seem to drop an enemy soldier with every shot. In some shots, the GI's rifles are not pointing even near where the Japanese soldiers are but the latter obligingly fall dead nonetheless.
Revealing mistake: The chimpanzee, Jebo, is wearing a dress and imitating dancing in one scene. As Jebo runs off, Jane exclaims "My dress.". There is NO WAY that dress could have fitted a grown woman. It is a pretty nice fit for the much smaller monkey, though.
Revealing mistake: After shooting in the door to Meg's office, the man in the darker jacket shoots the computer then steps into the room. John jumps him and grabs his gun (his shirt is unmarked in this shot). John then shoots him at point blank range. In the closeup of the shooting, the man's shirt is already torn - and the bloodpack/charge is visible through the hole - for a few frames before the gun is fired and the special effect goes off. (00:22:23)
Revealing mistake: The de Havilland Beaver takes off the first time for Makatea King Kong peak is in the background (a known peak on Kauai). When they land on Makatea there in the background is King Kong again, right where they took off from.
Revealing mistake: McClaren breaks out of a building through the picture window. The glass breaks not as a normal window would, but fragments, as if it were sugar glass or similar. It's really obvious.
Revealing mistake: When they are trying to escape the building, he throws what looks like a bollard at the glass door. The door shatters before the bollard hits it. (00:53:45)
Revealing mistake: In the scene on the freeway when the semi is sliding sideweays, if you look at the back wheels of the trailer, you can see the wheels making it track straight.
Revealing mistake: After the boat chase at the beginning, when the police officer turns the dead 'Sergi' over, you can see 'Sergi' lifting himself up with his hand on a rock before turning over. (00:04:00)
Revealing mistake: You can see the gun squib bulging out of the the police officer's right chest when he's shot. (01:31:05)
Revealing mistake: When Misty is setting the table, Brock's left foot clips through his cooking tool. (00:10:30)
Revealing mistake: When Todd is hitting the metal punchbag the first time, during the slow mo part you can see it flex as if it is made of rubber.