Deliberate mistake: In the scene where they break into the train from its roof, you can notice that despite the high speed and the consistent wind, Captain America's fellows have no difficulties in running, standing up still, and even jumping, like they felt no air resistance. Moreover, you can see that their hair is not moving at all, completely missing to realize any "windy" effect.
Deliberate mistake: During the cavalry charges, swords are held at shoulder height as they would for charging enemy cavalry, not knee height for charging infantry. This was a deliberate decision in order to have the blades more visible.
Deliberate mistake: There's no way the tip of a mast is strong enough to support an entire swinging ship, even if the latter one is a lot smaller. (01:00:00)
Deliberate mistake: In the opening title sequence, just after the title of the movie is shown, Puss cuts a P with his sabre into a curtain or flag. In the middle of the P, there is cloth remaining, but since he cuts edges all around this to make the Capital P, this cloth should fall away as it is no longer attached to anything, yet it floats in mid air.
Deliberate mistake: Right at the end of the film, the two Norwegians (Lars and Matias) are seen chasing after Lars' dog in a helicopter. Notice how their clothing and the interior of the helicopter are not the same as they looked in the original 1982 film by John Carpenter. It's supposed to be the same event.
Deliberate mistake: The agent is entering the office approaching his desk where a computer sits with the screen on depicting classified material. Computers left unattended go dark after x amount of time. This computer being in a federal FBI building should be logged out of and not open for everybody to see. (00:19:00)
Deliberate mistake: The scenes involving the 8mm projector and screen did not also contain legitimate light rays from the projector to screen or show any obstructions on the screen despite Joe or someone else between the projector and screen. What showed on the screen is what would be expected if using a videotape or DVD.