Disclaimer: Avatar is so not mine. Written for fun, not profit.
Obligatory ten-minute character study. Yeah, I dunno.
lessons in thin air
airbenders didn't like staircases (and they weren't too fond of handrails, either)
The Western Air Temple isn't really built upside-down - not unless airbenders normally put furniture on the ceiling - but all the same it's meant for a people with entirely different concepts of height and freefall. There are doors that open onto fifty-foot drops and gaps where bridges ought to be and a distressingly small number of handholds, and in the beginning Aang's forced to do most of the inevitable scavenging by virtue of the fact that he's the only one who can reach half the rooms.
On the hours-long trip to the Sun Warriors and their sprawling stone ruins, he admits to Zuko that he stuck everyone in what used to be the nursery.
"I thought it'd be more comfortable," he says with a quick cheerful shrug. He's only making conversation, after all.
Zuko hears-feels the flying bison rumble beneath him and thinks of a people who didn't so much live on the earth as temporarily touch down on it.
there's something to be said for domestic bliss
Despite his years in exile and all the time he spent wandering the Earth Kingdom (on a stolen ostrich-horse, no less) Zuko isn't entirely sure how to survive away from civilization. He's not the worst of them, not when Teo's there to look politely blank at anything that isn't a machine, but ultimately he has no idea how to hunt or fish in strange territory and only rudimentary knowledge of how to find water or forage.
But he's determined to learn, so he tags along with Aang and Haru in their quest for fruits and with Sokka on a fishing expedition. (The lemur stows away in Sokka's bag and manages to tangle itself and Zuko up in the line.) He helps start the fire for the one meal of the day, at least once Katara decides that maybe he won't try to poison them after all. He strings rope for makeshift handholds and and helps sort through dwindling supplies and listens in mostly-patient bafflement as Teo explains all the ways his balloon could be improved upon.
Once he catches the Duke swinging a pair of sticks around and shows him a few basic steps - how to avoid hitting himself in the head, for starters. He acquires a tagalong after that. (Jet also fought with two swords.)
a little humility never hurt anyone
It is strange and humbling and not a little annoying to realize that he's not the best bender in the group, even leaving aside the way Aang casually does the impossible on a regular basis. Toph will be something frightening when she's older - Toph is something frightening, twelve and very small for her age and probably his sister's equal - and there is nothing graceful or gentle about Katara's waterbending, which strikes with all the merciless swiftness of a typhoon.
He consoles himself with the fact that he's still the best with swords, at least until Sokka gets fed up with sparring him two weapons to one and attempts to bash him over the head with the boomerang.
the Fire Lord and the Bei Fongs are eighth cousins twice removed
Toph isn't necessarily the most welcoming of the group, less because of who he is than because there is some part of her that is always measuring and assessing and on her guard. All the same, her presence is strangely reassuring - the way she uses certain words, the way she was also required to memorize tediously dull classics as a child, the way she takes up space in that aggravating way only nobility can manage.
never turn your back on a waterbender with a grudge
His uncle says that waterbending is about balance and ebb and flow, but the way Katara fights is nothing like that. When she practices there is a terrible sort of power about her - the sort of all-consuming power he remembers from two years in exile, living at the mercy of the ocean and its storms.
No matter how much Katara may accept him one day, she will kill him - she will kill anyone - who lays a hand on Aang or her brother; she will act without a second thought and she will be merciless and deadly, consequences be damned.
Katara is very much like him, no matter how much either of them might hate to admit it. (Sometimes Katara is more the fierce unflinching warrior than her brother will ever be.)
when in doubt, feed the animals
For reasons Zuko's never entirely clear on, Aang's flying bison takes a liking to him, rumbling in a friendly sort of way whenever he walks by (and trying to lick him once, but he pushes Sokka into the line of fire). He winds up on the Appa-feeding roster early on, lugging hay over and even sneaking in a cautious pat on the nose when he's pretty sure no one's looking.
The lemur makes exasperated chittering noises at him until he bribes it with a piece of fruit. They get along fabulously after that.
the smartest person in the room won't shut up
One afternoon Teo and Sokka chase everyone away from the war balloon and proceed to scramble all over it, talking about weights and lift and other seemingly unconnected words strung together. It's all either of them will discuss for the rest of the night, and when Teo drops of to sleep first Sokka is back in the balloon, muttering out loud as he comes up with ways to make it better and faster and possibly add a battering ram - and a half-dozen ideas for fortifying an airbender temple against one, considered and examined for flaws and finally reworked into something newer and better.
Because the other boy's chatter is keeping him awake anyway, Zuko listens with half an ear and thinks of the would-have-been invasion.
He wonders if anyone realizes the remarkable thing about it: not that it failed, but just how close it came to succeeding.
the Avatar is (one hundred and) twelve years old
There are no skeletons in the Western Air Temple - but there are scorchmarks and ash here and there, some dusty tool or bit of broken jewelry burned and blackened beyond recognition.
Zuko is high in the air, somewhere in the bottom-top of the upside-down temple with his feet inches from a thirty-foot drop and his hands braced against a narrow doorway. Below is the great flurry of activity - earthbending lessons and tending to Appa and making repairs to the war balloon. The Avatar is somewhere in the middle of all this mess, flowing from one person to another, and if Zuko were more observant (but he isn't, not yet) he would understand why the empty temple seems louder and busier than the palace ever did.
It is old habit for him to think of the Avatar as aloof and ancient and all-knowing, cleverly disguised as a twelve-year-old boy.
It isn't much of a habit at all for him to think of Aang as something like a little brother (because this hasn't occurred to him yet, because he doesn't know what it means) - so instead he takes a shortcut through the temple to tell certain Avatars their break was up an hour ago.
His boots leave footprints in the ash.