One day little Johnny comes in from the play ground and write the word "penis" on the board in block letter very small. So the teacher comes in and erases it and looks around the class for a guilty face. So the next day he does it again but bigger and its taking up half of the board. So she erases it and looks around the class for a guilty face and doesn't find one. So finally the third day little Johnny write penis on the board in big block letters covering the whole board. The teachers erases it and says "what's up with this word?" Little Johnny stands up and say "the more you rub it the bigger it gets".