Sarcasm is an adjusted stress reaction.

Oh hai! Does this ring a bell: an AU where Azula never discovers Zuko and Iroh are in Ba Sing Se, and years later Zuko is raising his secret-Firebender daughter (whose mother is Jin) when he's reunited with Mai?

I had the idea, or so I thought, but now I've become paranoid that I'm actually remembering someone else's fic.