little johnny's fly

Little Johnny and the other kids were playing at school when little Susie walks by and unzips Johnny's fly.
He went home and told his mother about it and she said, "Tell the little girl not to do that again because you have a mouse in your pants."
The following day little Susie runs over and does the same thing again. As his mother told him, he exclaimed "Don't do that because I have a mouse in my pants."
At that remark, Susie lifted her skirt and said, "Go get 'em Pussy."