An old grade school prank. You'd write Pen 14 on your hand and walk up to an unsuspecting schoolmate and ask him if he wanted to join telling him he could be Pen 15. You'd then write Pen 15 on his hand, and everyone would laugh at him.
"I'm in the Pen club. I'm Pen 14, you can be Pen 15."
by Ritley August 24, 2003