When you witness or do something that is Larry David funny. To be Larry David funny it has to be funnier than just funny, and after telling someone about it they laugh profusely as well.
Man 1: What's so funny?
Man 2: I slept at this random girls place last night and when I woke up hungover the next morning I couldn't remember what I did with my phone. After searching for it extensively we finally gave up and she said, "If I find it, I'll just give you a call." And yes, she was serious.
Man 1: Hahahaha that's hi-larry-ous!