a little boy walks into his parents room to see his mum on top of his dad bouncing up and down. the parents stop and his mum quickly dismounts, pulling the covers around her.

"what were you and dad doing?" the boy asks his mum.

"well, your dad has a big tummy and sometimes i have to get on top of it to help flatten it," she explains.

"your wasting your time," says the boy. "when you go shopping, the lady next door gets on her knees and blows it right back up."