A teacher walked in and saw on the blackboard... "PENIS" written very small. She erased it off and left. The next time she came in the class, she saw "PENIS" written on the blackboard again. Only this time, it was a big bigger than before. She erased it again and asked who was doing it. No one said a thing. Every time she came in class, it was the same... but bigger and bigger. Finally, she came in class to expect it being really big... but instead... she got a different message. "The more you rub it, the bigger it gets!"