Superman II (1980)

Deliberate mistake: When the villains rampage the White House, the flag's base remains on the ceiling, and the flag pole falls inside the house. So the final scene with Superman carrying the flag and its base as if it had been previously stolen or destroyed, is nonsensical, but it looks very patriotic indeed.

Sacha

Deliberate mistake: The kid who falls into Niagara Falls spends 28 seconds falling before Superman catches him. Niagara Falls is 51 meters in total height. Considering how fast something falls, the kid should have hit the water long before Superman ever entered the scene. (00:39:30 - 00:40:00)

Deliberate mistake: French officers and firemen speak in English between them.

Sacha

Deliberate mistake: One shot of the kid falling into the Niagara Falls is used twice. The first time, the shot is used after Lois notices the kid falling. The second time, the same shot is used after the kid's parents look over the edge of the falls. (00:39:30)

Deliberate mistake: Luthor and Teschmaker visit the North Pole protecting themselves against the cold. Lois manages to wander around with a mere, but sexy, shirt.

Sacha