A couple were in their bed ready to make love when their four year old son walked in and asked, "Daddy can I ride on your back?"
The dad said no, but the wife said, "It's OK honey he doesn't know what's going on." So the son rode daddy while the couple continued making love.
Soon the wife started moaning and breathing heavily, the little boy yelled, "Daddy you better hold on. When she did that yesterday me and the milkman both almost hit the floor!"