An Art professor had allowed his students to mail in their final exam artwork rather than coming to class to turn them in. The professor had assigned 3 peices of art to be done, one of them could be anything the student chose to do.

After one student mailed the artwork a reply came from the professor, "I only recieved two peices of your work. Where is the third?"
The student replied,"Look closely at the stamp!"

(I don't know id it is a true story but I found it funny when I read it years ago)