i got one.

one day a teacher walks into her classroom to see the word "penus" written on her board in 3 inch high letters. annoyed she quickly grabbed the board cleaner and rubbed it out.

the next day the same teacher went into the same classroom and found the word "penus" once again written on the board, except this time the letters were 5 inches high. once again, she rubbed the word out.

the third day the teacher came into her classroom to once again find the word "penus" wirtten on the board, this time the letter were 7 inches high. she rubbed the word out again.

the fourth day to teacher walked into her classroom once again expected to see "penus" written on the board. to her surprise she found something else was written there:

"the more you rub it, the bigger it gets!!"