Deliberate mistake: When "Legs" lowers the Pez duck named Ducky down through the removed lightbulb hole, to ring the doorbell, the lightbulb housing is bigger than the hole but they bring it up through the hole to remove it. (01:03:55)
Deliberate mistake: Near the end of the movie, there is a shot of the "Iwo Jima" with the two recovery helicopters taking off. For a moment, you can see the number 11 on the inboard side of the ship's island, which identifies it as the USS New Orleans (LPH-11), a sister of the Iwo Jima. Admittedly, it was the best the producers could do, since by the time the movie was made, the Iwo Jima (LPH-2) had been decommissioned.
Deliberate mistake: The huge bruise on Tommy's face, from the board hitting him, disappears in less than a day.
Deliberate mistake: In the scene where the characters are initially signing up for the contest, Gene Hackman's henchmen cock their weapons as they enter, then after Sharon Stone shoots the rope apart the henchmen cock their rifles again. The problem is that with a second cocking the rifles would be ejecting any chambered brass. It seems like a deliberate mistake because they cock their rifles an inordinate number of times throughout the movie; I would guess the director wanted the effect of hearing the weapons being cocked multiple times at the expense of continuity with the rifles.
Deliberate mistake: After our heroes jump from the plane.as they are landing their parachutes the each come to a soft standing landing. if you jump with a standard Dash 1 Bravo parachute (which none of them had) your landing is similar to jumping from 14 feet high with no chute: you hit like a rock and collapse (the Parachute Landing Fall or PLF) They were all using stunt parachutes of a type that was unavailable in 1968.
Deliberate mistake: When the house is splitting in two, the board game should have fallen long before it actually does. (01:25:25)
Deliberate mistake: Throughout the entire movie every character seems to speak fluent English, despite several portions of the movie take place in remote Russian locations.