Father and mother are making love in the bedroom.
Mother is on top of father.
Suddenly the son enters the bedroom.
Everyone is embarrassed, of course.
The next morning, the mother takes the little boy aside and says,
“I’ll tell you about what you saw yesterday, you know Dad has a big belly and that’s why mom sometimes sits on top of that belly to push it flat.” .
Says that little boy: “But mama, that does not make any difference.”
“Oh no?” the mom asks. “
No,” says the little boy,
“When you go to work, the neighbor comes, and she puts herself on her knees for Dad, and she blows his belly up again!”