Continuity mistake: When Scrooge tells Crachit to shut the door because he's letting the heat out, there is nothing in front of Scrooge on the desk, but in the next shot gold coins have appeared.
Continuity mistake: When Scrooge asks the ghost "Down there?", the door behind him is closed, but in the next shot the door is open.
Continuity mistake: Before going to bed, Scrooge takes off his slippers and puts them by the side of his bed. But when he is disturbed by the singers, the slippers and the pillows he is resting his head on have disappeared.