Continuity mistake: Mr. Bean puts Christmas cards in envelopes, then seals each envelope by licking each flap. Then he puts the envelopes through the mail slot in his door, pretending that someone else mailed them to him, which is funny. Then he opens each envelope just by unfolding the flap instead of tearing open the envelope, that means that each flap had not been sealed.
Continuity mistake: After Mr. Bean's musical performance, there's a shot of people applauding him. There's a man at the right of the group. In the next scene that same man is seen buying the last two Christmas trees, right before Mr. Bean gets a chance to buy any. There's only five seconds between the scenes. The man couldn't have run to the Christmas tree salesman, talk to him, and pay him for the trees within those five seconds. (00:10:25)