Other mistake: When Kevin first enters the hotel, he is told to get to the lobby he should go straight ahead and turn left. The next shot shows him turning right into the lobby.
Other mistake: Near the beginning, Scrooge leaves Scrooge and Marley and walks home. As a result, Bob Cratchit and the bookkeepers clean up, and Bob Cratchit locks up with a key. Yet the next day, when Scrooge gives gifts to the other bookkeepers, not only is Scrooge able to get inside without a key, the door is unlocked as well. (00:16:45 - 01:16:05)
Other mistake: When the Penguin is talking on the staircase to his audience of voters, he gives a badge to one young woman. As he lifts it up it is clearly a pin-on design button, however the Penguin leans forward as presses the badge against her blouse as if it were a stick-on design. The badge then stays on the blouse and doesn't fall. (01:00:30)