Q:How many presents can Santa fit in his empty sack? A:Only one. After that it is not empty anymore!\nWhat do you think is the punchline of the above joke?
Explanation:The old empty sack trick! This joke plays on the understanding of the words “empty” and “how many.” The listener expects the answer to be a number, not an explanation. But it is true- if there is one gift in the sack it is no longer empty.