Barney: Not possible. You cannot have sex on a windsurfing board.
Lily: How do you know?
Barney: Glad you asked Lily. I have crafted a list of every vehicle, land-based, aquatic and airborne in which/on which it's possible to have sex. And of those 33 vehicles, I have had sex in/on 31. Windsurfing board, not on the list, not possible. Oh, P.S., in order to hit 33, all I need is bobsled and the Apollo 11 space capsule.
Lily: To get that last one, you'd have to break into the Smithsonian.
Barney: This conversation never happened.