Secret Detective

When you are banging a girl, and you have your friend hide in the closet, and while you are banging her up the butt, you pretends that your penis slips out, and then your friend quickly rushes to the scene and starts banging her up the butt. Then you leave the room, and go by a window which she is facing, and then you wave to her or do something noticable, and then she realizes, "Who's banging me?"