A little boy walks into his parent's room to see his mom on top of
his dad bouncing up and down. The mom sees her son and quickly
dismounts.
Worried about what her son has seen. She dress's quickly and goes
to find him. The son sees his mom and asks' "What were you and dad
doing?"
The mother replies "Well you know your dad has a big tummy and
sometimes I have to get on top of it to help flatten it."
"You're wasting your time." says the boy.
"Why is that?" asked him mom, puzzled.
"Well when you go shopping the lady next door comes over and gets
on her knees and blows it right back up."