When your droopy balls smack against someone's pussy.
Guy 1: You know when you jump into a cold pool and your nuts cling to your body because they want warmth because your sperm wants to be warm.
Guy 2: I don't think I know that.
Guy 1: Yeah, nuts shrivel...
Guy 2: Oooooh yeah.
Guy 1: But when it's warm, they like, droop...
Guy 2: Oh...
Guy 1: And then they act as... they act as like a Pussy whacker.
Guy 2: (Laughs)
Guy 1: When you're doing it doggie style.