Disclaimer: Avatar is not mine. It's Nickelodeon's. Blah blah blah ad nauseum.

Author's Notes: Takes place several years post-series.

I really thought for a while that I was the only one to have this theory. Silly me, of course not. But I did come up with it on my own, not from anyone else's input. So there.

The First Airbender

The winds of autumn were high and strong in the Biyang mountains, and Avatar Aang's robes blew about him wildly. The sixteen-year old leaned forward, his body angled dangerously far away from the safety of Appa's head, until it seemed as though it wasn't gravity at all that kept him from falling. He grinned.

"Almost there, buddy," he said, looking down at his bison's enormous eye. "Wow. It seems like forever since we've been here."

The bison replied with a low groan, and from behind the Avatar's head came a high-pitched chitter.

"Well, yeah, they know I'm coming," said Aang with a shrug. "I sent the last hawk a week ago."

Two bright yellow eyes glared balefully from the warmth of the blankets in Appa's saddle, before a small furred hand pulled one down and covered them. Aang laughed.

"Oh, come on Momo! You've stood through worse weather than this!" The lemur, who as he aged seemed to more and more prefer the warmth of the saddlebags to Aang's shoulder, did not reply.

"Suit yourself. But you're missing a great view."

It was if anything, an understatement. The Biyang mountains were often clouded, but today the fall sun shone brightly, illuminating the softly forested mountainsides, the sheer cliffs of granite, and the stark rivers that cascaded down the steep slopes. It was enough to make a resident of flatter landscapes' eyes bulge, but to Aang it was the topography of home.

Aang checked his position by the sun, but knew that he didn't really have to. Appa knew the way.

As the mountain that held the Northern Air Temple came into view, Aang fancied that he could see small specks flying around it, spiraling down and soaring on hot air. The Avatar hummed to himself. Soon, they'd be soaring on more than that.

As Aang drew closer to the main plaza of the Northern Air Temple, he could see that a large crowd had gathered. He could hear the cheering from quite a distance, and by the time he landed it was almost deafening.

"Hello, hello, yes, hi, pleased to meet you, yes, that's a lovely baby ma'am, hi there, hello…."

Aang fended off the grabbing hands of the Northern Air Temple's residents. Was it just his memory failing him, or were there more people here now than last time? The crowd surrounded Aang, their hands reaching out to touch his robes. It was a bit disturbing, but not unexpected for the Avatar. He'd had similar receptions elsewhere. The trick was to dodge the clutching fingers so as not to lose any clothing, while at the same time being warm and friendly.

"Yes, yes, pleasure to be here, hey, hello…"

The Avatar's eyes finally homed in on a balding head of spiky hair shot through with grey, and he began moving in that direction.

"Welcome, Avatar Aang," said the owner of the hair, the Mechanist.

Teo waved by his father's side. "Hey Aang."

"Hey," said Aang, somewhat breathlessly, then turned around to address the crowd. "I am going to speak to the Mechanist and Teo in private," he said, and the crowd leaned forward. "But I promise I will address your concerns at a later date."

The crowd muttered in disappointment, but slowly dispersed. Aang turned back to the Mechanist and Teo with a sigh. "I never really get used to that."

The Mechanist smiled, wrinkles crinkling around his eyes. "We weren't expecting you for another few days, so your early arrival is quite the cause for excitement."

"Well, we had a pretty good tailwind."

"It's fine," said the Mechanist. "We already have a room for you, and we cleared the stable for Appa."

"Or rather I did," said Teo. "Dad almost forgot you were coming."

Teo's father laughed. "It's true! I can't deny it."

Aang smiled. "So how have you two been?"

"Well, Teo and I have been working on a fascinating new project," said the Mechanist excitedly. "A while back, right after the war ended, I visited Ba Sing Se, and I was struck by their system of public trolleys. So I thought to myself: Imagine if there was a system like that across the whole Earth Kingdom! And fueled by coal, not earthbending, so anyone could use it! What a grand construct that could be! We'd have to build special roads for it, of course, but imagine how easy travel would become!"

"Uh, yeah, that sounds nice," said Aang, imagining smoke-belching machines covering the landscape. But the Mechanist was helping him; he should be polite.

"Yes, the applications…"

"How have you been, Aang?" asked Teo, cutting off his father before he could gather steam.

"Busy," said Aang, allowing his weariness to surface for a moment. "You have no idea. It feels like I never have any free time. Everyone wants my help all the time. Between the Fire Nation and Omashu and the Northern Water Tribe and Ba Sing Se and every little village I go through… I don't know how the other Avatars handled it."

Teo gave a low whistle. "Wow. That's a lot."

"Yeah. The three Nations have been taking up so much of my time…" Aang smiled. "I've hardly had any chance to give my attention to the fourth."

Teo smiled, but the Mechanist's brow wrinkled. "Aang," he said. "We are happy to be the subject of your experiment, but we are not Air Nomads."

"You're all I have," said Aang simply, his face suddenly solemn. "You're the best I have." Then his expression switched back to the cheerful countenance that his friends were used to. "But that doesn't matter. You guys said that there were some volunteers?"

"Yeah," said Teo. "And actually…" He looked up at his father, who smiled, almost sadly, and nodded. The crippled young man took a deep breath. "Aang. I know I'm not… I mean, I'm not the best person for your experiment. But… I was wondering if… if you would… I'll understand if you…"

"Teo," said Aang gently, "I don't mind. I would be honored if you would be the first airbender."

After the war, the central sanctum of the Northern Air Temple was cleared of the machines of war it had once sheltered, and even the Mechanist's continual improvements had not dared touch it again. Aang closed the door as soon as Teo wheeled in. "We should have privacy in here," said Teo. "Most people still have a hard time working the doors."

Aang nodded. "Good. This technique is a bit… showy. I don't want people getting the wrong idea."

Teo grunted and scratched his head. "So… how is this going to work, exactly?"

"I'm going to bend your spirit."

At the look of alarm on Teo's face, Aang quickly waved his arms. "No, no, it's not like that. It's just a little tweaking, to connect your inner elements to the outer ones. Just… tinkering a bit with your chi."

Teo's expression relaxed a hair, the machine-based metaphor sitting well with him. "Will that hurt?"

Aang frowned. "I don't think so. I've tried it out on Momo, and he seemed alright."

"On Momo."

"Yeah. There's no difference, really. I mean, he could fly and stuff before, so you can't really tell."

"On Momo?"

"Yes. Animals have spirits too you know," said Aang indignantly. "They're a little different, but they're there."

Teo groaned. "Okay. Okay. If you're sure. What am I supposed to do?"

"Just… relax. It will feel kind of… weird. But if you let me do it, it shouldn't be too bad."

Teo took a deep breath. "Alright."

"Oh, also, you need to take off your shirt."

Teo raised his eyebrows. "Al…right."

After Teo shed his shirt and placed it on the ground, Aang stepped forward and placed his hands above Teo's brow and heart. He could feel how hard it was beating. "Are you ready?"

"As ready as I'll ever be."

Aang closed his eyes, and reached into that part of himself that the Lion Turtle had placed within him. Almost immediately, the power flooded him, filling his entire being with crackling, roaring, flowing, rushing chi. The world around him had changed, from the deep shadows and ancient stone of the Air Temple sanctuary to a blazing spectacle of light and energy. The stones had energy, the air had energy, the tiny insects that crawled in the cracks had energy. It was two-toned, beautiful, breathtaking, and it shone through Aang, filling him to the brim.

The Avatar reached out with arms that were not arms, toward the center of brilliant energy that lay in front of him. He could see Teo's chakras, strung together like beads on a string, spinning deep within him, and moved his awareness into them. He had only done this once before with a human being, and the energy within Ozai's chakras had pushed back, had tried to force itself into Aang's body and twist it to its own purpose. Aang still shuddered at the memory.

How different this was! While bending Ozai had been an invasion, Aang's spirit moved into Teo's body without resistance, without struggle. Aang moved up, from the Earth Chakra of Survival (Long buried memories of water and pain and limbs askew) to the Water Chakra of Pleasure (the exhilaration of flight) to the Fire Chakra of Will (caught without my chair, dad doesn't know where I am, but I will reach him, if I have to drag myself across the temple) to the Air Chakra of Love (Mama…) to the Sound Chakra of Truth (my father builds weapons, but he's not going to use them) to the Light Chakra of Insight (who says the Earth Kingdom can't fly?) to the Thought Chakra of Detachment (for my Nation, I will leave my home and give my life). And then, once the Avatar had taken over Teo's energy in its entirety, he was ready. Here, Air, he thought (or was it Teo's thought? He couldn't tell the difference). He moved the energy of the sky and wind into Teo, until it flowed through the other boy's chakras like a river.

Aang let go, and his spirit immediately snapped back to his own body with an almost audible whoosh. His whole body ached like he'd run a marathon, and he dropped down to his knees with a groan.

"That… it… that should do it." he gasped, wondering how much time had gone by.

"Guh," replied Teo. "Bluh uhhh. That wuh… was really something."

Aang shook his head to clear it of fuzz. "You okay?"

"I… uh. I think so." A pause. Then, almost disappointedly, "I don't feel any different. Just tired."

"That's actually good. It means I didn't change anything I didn't mean to." Aang slowly got to his feet, wiped the sweat from his brow, and handed Teo back his shirt. "But try this, just for a second."

Aang held his hands a few inches apart, and moved them as though they rolled a ball of invisible clay between them. Then he moved one palm forward, and Teo felt a sharp breeze blow into his face.

Teo blinked. "Aang, I don't think I can…"

"Try it. Try feeling the movement of the air."

"I know how air moves."

"Don't know it. Feel it."

Teo looked at Aang skeptically, then moved his hands clumsily. His look of incredulity slowly turned to one of fascination, and he rolled the invisible ball for much longer than Aang had. Then he turned one hand out, and Aang felt the briefest ghost of a breath on his face.

The Avatar gasped. "You did it," he said, sounding like he hardly believed it himself. "You did it. You did it, Teo! You're an airbender!"

The last airbender grinned like the sun itself, and the first airbender returned it, eyes shining.

A/N: What's that? A happy ending, from me? I know, crazy right?