The promise mentioned in the summary is from the end of Bato of the Water Tribe. If you are not comfortable with the idea of two guys kissing, then you should steer clear and read something else.
Yes, I own Avatar, but Nickolodeon didn't like my ideas, so they changed the title from Cooking with Nuclear Physisists and made it a cartoon and removed all my characters.

Faded and peeling, barely visible under the more recent posters, a notice of the disappearance of the fire lord's youngest child gazed dolefully at passing travelers. The face was that of a younger child, aware of the world but not yet quite of a discernable gender, which was not aided by the red fire scarred scalp. A date from several years ago was stamped in one corner.

Another bald child, this one possessing an arrow tattoo to make up for the lack of hair, ran to the board to check the current bounty on his head. His eyes roamed across the other notes and found the hidden paper.

"How much are you worth now?" his male companion asked, picking white hairs from his heavy blue garb much more comfortable in the arctic conditions either ice kingdom rather than the temperate earth kingdoms.

"Too many figures to count right now," he child replied as a lemur scrambled onto his shoulder. "But look at this!"

The other boy gazed at the board for a moment. "The fire nation doesn't take good of children."

"It's royalty!" No change in expression. "He...she...it knows the secrets of the nation!"

"It's probably dead now," Sokka said dismissively. "Let's just get the town already."

Aang took a last look at the sign before following his friend.

AVATAR

A smarting remark against his masculinity had sent Sokka on a search to prove them wrong. This train of thought brought him to a rather noisy pub with a brawny man crying by the door.

"You've still got five more minutes out there, Yord." This voice cut through the rest, carrying an air of command.

As his eyes adjusted to the gloom within, he found himself drawn to the far side of the room. Partly it was to escape the drunken singing by the door, but mainly to get closer to the gorgeous barmaid. She filled his world completely like she filled a tankard. Her muscles weren't bulging, simply large enough to make her duties manageable. Yes, he had fallen, and rather hard.

"What can I get you?" she asked with a sweet smile, breaking into his reverie.

A blush rising on his cheeks, he managed, " Hi, I'm new in town. Could you show me around?"

His face grew hotter as she looked him over. "I can't leave the pub anytime soon, but if you're willing to wait a few minutes, I could talk you through the area."

"Thank you," he replied. Perhaps a little too loudly, for some of the closer patrons sent up catcalls. She easily silenced them by throwing a wickedly sharp knife in their direction with enough force to lodge it in the wall. Multiple scars littered the area around it, as though this was a normal occurrence. He smiled to himself, walking a little taller.

Several moments later, she slid onto the bench opposite. One hand gripped a piece of chalk, the other another steak knife.

"You're a long way from the arctics," she said with a smile.

"Oh, yeah," he gushed, unable to contain himself. "I've been traveling with the avatar for awhile now."

"So he is back?"

He laughed kindly. "He's been back. Where do you get your news?'

"Drunk people," she conceded. "What sights have you seen?"

He launched into a detailed account of their most exciting (as well as his most flattering) experiences. She hung on to his every word, responding appropriately every time.

"Enough about me," he sighed at last. "How about you?"

Modestly, she told her tale of growing up on a farm. After the crops and the fields burned, killing their only source of income ("dad dropped a lit pipe during the drought," she insisted as his eyes grew steely with murderous anger), she had struck out on her own and started this pub. From there, the conversation progressed into directions around town. He was leaning over the diagrams she drew on the table when he realized she had paused. Slowly he raised his head, a pleasant blush settling in as he felt her close proximity. For a moment, their eyes met, but then she closed his, he followed suit and–

–the door slammed open, as did they eyes.

With a sigh, she got to her feet. "Let me take care of this." louder, in a tone the caused a good number of the patrons to flinch (the exceptions being those who were either far too drunk or unconscious), she roared: "if you came to cause trouble–"

the familiar voice of Prince Zuko sprang in: "I have full backing from the fire nation–" Pause, then in a higher and far more distressed voice, "Why are you wearing a dress?"

"Haven't you ever seen a lady?" someone leered to many hoots.

"the fire nation ships their boys off to war before they see their mothers!" another voice roared before the owner slumped to the grass-strewn floor.

"My brother's hair caught fire when we were younger," Zuko insisted. "His scalp burned and he was unable to grow hair again." Their was a collective gasp and some of the men began to cry while others ran out the door.

Sokka scoffed and turned to look.

Their stood the pretty barmaid with her hair.

Except it was in her hand. And her head was a shiny pink.

"Guess I won't be needing these anymore," she muttered. One hand pulled at the neck of her dress, allowing the other to plunge in and retrieve two large oranges. These she tossed to a table of salty-smelling men covered in jewelry. Zuko cleared his throat. "The dress stays."

"So who kidnaped you?" he asked, hands lighting.

"I ran away after you were banished," she explained. "I didn't want to take your place."

A teary moment hung in the air before the prince embraced the princess.

Sokka's mind shattered at last. They were bother princes.

"Come on," Zuko said at last, pulling away. "Why don't you show me around?"

The transvestite turned to look at Sokka. For a moment their eyes met, though she looked away first. Sokka knew what he needed to do.

Burying his own doubts and feelings of squickiness, he rose and walked over to the reunited family. One arm fell onto the bartender's shoulder and he smiled. "I'll catch up with you later, Kiozu."

AVATAR

The Avatar Alliance, for lack of better term at this point, had regrouped and was traveling deeper into the town together.

"Zuko's wearing a dress!" Aang suddenly exclaimed, pointing excitedly.

Indeed, the prince had on a light blue sun dress with several embroidered flowers. Beside him stood another, this one in a fiery skirt and matching tunic. Like the puppy he was, the avatar bounded forward lightly, barely touching the ground.

"Zuko, why are you wearing a dress?"

"Leave me alone, Avatar," Zuko growled, inspecting his reflection. "I'm spending the day with my little brother."

"Your brother looks like a girl," Aang said with the honesty that lived with naivety. "Why is he wearing a skirt?"

Before his simple clothes were lit by Zuko's angry outburst of flame, Sokka jogged over and planted a kiss on Kiozu's cheek. "How has your day been?"

"Sokka, you know that's a boy," the avatar pointed out, only to be told, "Yeah, I know." There was a moment as he considered this, then he floated up to kiss Zuko's cheek. "Katara told me to give you that," he explained.

"How...very kind of her," Zuko said carefully.

A thump from behind informed them Katara's brain had reached its limits.