sound coming from his parents room.  Finally one morning he goes to
     his mom and says, "Mommy, every night I hear you and daddy making
     noises and when I look in your bedroom you're  bouncing up and down on
     him." His mom is taken by surprise and says, "Oh... well...ah....well
     I'm bouncing on his stomach because he's fat and that makes him thin
     again."  And the boy says, Well, that won't work!"  His mom says,
     "Why?!?"  And the boy replies, "Because the lady next door comes by
     after you leave each day and blows him back up!"