Quote from Phoebe in The One with Monica's Thunder
Monica: Hey, Pheebs, what's up? Phoebe: You said I could sing at your wedding, so I'm going to need a small deposit. Monica: What? Phoebe: You know, just some good-faith money to hold the date. Chandler: We're not giving you a deposit for our wedding. Phoebe: Oh, I see.