Deliberate mistake: While most of the German spoken in the movie is correct (even if with bad accent) there is a translation error in the scene at Yankee Stadium. The accent suggests that these bad guys were raised in the communist eastern Germany and previously served in the secret service "stasi." When the guy with the sniper rifle gets nervous and asks if he should shoot or not, the other one says,"Nein, wir brauchen den anderen", which would translate, "No, we need the other one", but the subtitles say, "We'll follow him", which they do.
Deliberate mistake: During Dade's first 'hacking' scene, he is wearing sunglasses. The shades disappear for a closeup shot of Dade's eyes and a brief montage of TV clips, then reappear on Dade's face in the longer shot. (00:05:45)
Deliberate mistake: In one of the scenes where Johnny Depp goes into the bathroom (specifically, when he changes clothes with the other man), Christopher Walken's character looks under the stall. The camera then shows the legs and crotch of a man sitting on the toilet, who still has his boxers fully on, but his pants are down.
Suggested correction: That man was not actually using the toilet. He was posing as Watson (Depp) so that Walken would think he was in the stall the whole time.