Quote from Phoebe in The One with Chandler's Dad
Joey: Pheebs, you know how when you're wearing pants and you lean forward I check out your underwear? Well, when Jake did it I saw that he was wearing women's underwear. Phoebe: I know. They were mine. Joey: Oh! No, no, wait. That's weird. Phoebe: No, it's not. We were just goofing around, and I dared him to try them on. Joey: That's weird! Phoebe: I'm wearing his briefs right now. Joey: That's kind of hot. Phoebe: I think so too. And that little flap? Great for holding my lipstick.