Thanks be to Douglas Adams for one particular line.
Katara
"So this is your girlfriend. No wonder she left, she's way too pretty for you."
It was the constant teasing she couldn't put up with.
Sokka, day in and day out with the girlfriend thing.
"Oh, look Katara, it's a ship on the horizon! You think your boyfriend's coming to get us?"
"Gee, if Katara's boyfriend were here we could use him for bait to distract the man-eating bears."
"Katara's boyfriend will be the first one with his back against the wall when the revolution comes. And then we can poke him with big sticks and stuff."
Stupid Sokka. She was tired and grouchy and sooooooo didn't need to hear this right now.
"How nice of your boyfriend to trap us all in a cave and then knock out the only Earthbender around for fifty miles."
"She's not my girlfriend!" Zuko snapped before Katara could.
The silence that followed that too-quick reply was significantly more awkward than any of the previous silences.
Stupid firebender. "Yeah, well, I'm too pretty for you anyway."