Adult Humor

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 dresses 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 as a big tummy and sometimes
I have to get on top and help flatten it."

"You're wasting your time," said the boy.

"Why is that?" the mom asked puzzled.

"Well when you go shopping the lady next door comes over and gets on her
knees and blows it right back up."