"It's SHOES, Elphaba. Let GO, already." Considering how dark a moment this is in the middle of...absolutely HILARIOUS!
Galinda: Now, let's tell each other a secret that we've never told anyone before! Fiyero and I are getting married!
Elphaba: He's asked you already?
Galinda: (gleefully) Oh, he doesn't know yet!
Fiyero literally (at least in some productions) comes swinging onto the scene, screaming "LET THE GREEN GIRL GO!" It's hilarious, considering how serious the scene is...as is the catfight between Glinda and Elphaba beforehand.
The following exchange between Elphie and Glinda:
Glinda: And what have you accomplished besides flying around on that mangy old thing!?
Elpheba: Well we can't all come and go by bubble! Who's idea was that? The Wizard's? Of course! Even if it weren't he'd still take credit for it.
Elpheba: Oh ho. Listen, I know that it is difficult for that blissful little blonde brain of yours to comprehend that someone like him could choose someone like me! But it's real, it's happened, and you can wave that rediculous little wand of yours all you want you can't change it! He doesn't belong to you, he doesn't love you! He loves me!
From the book, when poor Boq confesses his feelings to Galinda, and Elphaba is snarking at him the whole way for sounding rehearsed. Galinda scolds her, while at the same point ripping on Boq with "Let me consider his stupid idea", while he's still sitting right there.