It's not possible! You cannot have sex on a windsurfing board! ...
Barney: It's 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 all vehicles, land-based, aquatic, and airborne, in which / on which it is possible to have sex. Of these 33, I have had sex in / on 31. Windsurfing board: not on the list. Oh, PS 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.