A man is away on a business trip.  His wife is in the master bedroom, putting on a sexy dress, to see her new lover.  Their son is in the living room, playing with his toy trucks.  Suddenly, a car pulls into the driveway, and there's a knock on the front door.  The little boy opens it, and sees a strange man, with big muscles, wearing jeans and a tank top.
"Hi, mister", the boy asks.  "Are you my new babysitter?"
"No, I'm your new motherf*cker!"