little johnny at camp

One night Little Johnny was really scared sleeping by himself at camp, so he sprints out of his tent and runs to his teachers tent and asks "Miss can I please sleep with you tonight ?". His teacher replies "NO" Johnny moans and says "But my mummy lets me". "OK then, just for tonight" the teacher replies. Johnny jumps into bed with her and asks "Miss can I please play with your belly button with my finger". She again says "NO". "But my mummy lets me" says Johnny again. "Well I suppose it's OK" replies the teacher. Things are silent for a few minutes until the teacher leaps up screaming "THAT'S NOT MY BELLY BUTTON" Little Johnny replies "It aint my finger either"