The Spirits can be awfully stingy. For the wedding of the Moon, they permitted Sokka to invite one other mortal.
Sokka pounced on the word "mortal" and argued that the Avatar didn't count, because the Avatar was one of the Capital-S-Spirit-Immortals. He argued his point so thoroughly that eventually even the Ocean relented, and Sokka could invite the Avatar along with one other mortal.
Sokka invited his sister.
Seven days before the Winter Solstice, Katara and Aang reached the Southern Water Tribe. Sokka met them at the very edge of the wharf.
After three restful days, the three travelers outfitted themselves in their warmest gear and set out on foot eastward, along the coast. If they stayed on that path, they would eventually reach a village called Sedna; but they were not to stay on the path. They walked until they came upon an ancient cairn of pale stones, about four feet high.
Aang stopped beside the cairn, and looked out to sea. "I see it," he said. "The path to the Moon's Country."
Katara stood beside him. "I see it too!" She traced it with a gloved hand: the path lay precisely along the moon's trajectory, shimmering above the water.
The path's guardian spirit manifested (she had the shape of a leopard-porpoise) and squeaked a welcome at Sokka.
"Hello, how're you doing?" Sokka asked the guardian. To Katara and Aang he said, "C'mon, no time to lose," and stepped onto the silvery path.
Three days later, at the Winter Solstice…
The three mortals knelt in the great room of the Moon's house. Aang and Katara both wore Water Tribe robes, and plenty of layers; it is very cold in the Moon's country.
As for Sokka, he sat quite still and proud in his kuspak trimmed with wolf fur. He was entirely calm in awaiting his bride.
The Moon Spirit Yue's kindliness had won her many friends among the spirits, so there was quite a diverse crowd in the hall. A few guests were there to honor Sokka and his companions: the Painted Lady in her rags of silk, and Hei Bai of the forest; even the Blue Spirit, tall and spare as a winter tree, lurked in a corner.
It must be admitted, some spirits regarded Sokka with open curiosity, even a touch of contempt. Who was this uppity mortal? Sokka knew this; he kept his chin held high.
At the room's center, there was the Rabbit in the Moon (white, with black spots and a purple robe) tending an incense burner and the wedding altar, and near her sat the Ocean Spirit, the only one wearing black. His form was that of a tall and broad Tribal man, with a mane of black hair ribboned with kelp and coral beads.
The Rabbit in the Moon flicked an ear. "I hear the bride; she's in position," she said to no one in particular. "Well, let's get this show going."
She picked up a mallet and rang a gong on the altar. The congregation fell quiet.
A door slid open, and the wind that entered was so cold, so bitter, that even the Ocean shivered.
And there, outlined against a sky frosted in stars, stood Yue. She wore lavender and silver and white. Moonstones clasped her white hair, and her blue eyes shone. She stepped so lightly that she seemed to float.
Sokka looked at her and his stern expression melted. Yue smiled at him as she approached—
And then, by the Ocean spirit, the bride halted. Standing on tiptoe, she kissed the Ocean's cheek and whispered something. It was a chaste kiss, such as one given without grudge to an old friend. Then she went to Sokka and knelt beside him.
The Rabbit began the wedding ceremony by reaching into her robes and pulling out a pair of spectacles.
"Aiya," said the Rabbit, adjusting them on her nose, "I must say, Sokka, these little tchotchkes you made for me are just the thing. I haven't seen this well in decades."
Sokka just smiled in response. Yue reached out and took his hands.
The Rabbit rang the gong once more, and the ceremony began. "Hear me!" declared the Rabbit. "There is a young Spirit here. She wishes to be a bride, and to hold fast to this mortal. Who will vouch for her?"
"I will vouch for her!" said Katara, in a confident voice.
"Thank you," the Rabbit acknowledged. "Hear me! There is a mortal here, who wishes to be a husband. He would hold fast to this woman, despite, well, a few glaring discrepancies. Who will vouch for him?"
"I will vouch for him," said Aang.
"Well, the Avatar is good enough for me. Now, you two," the rabbit said to Sokka and the Moon Spirit…
The rabbit began to brusquely list out vows and the holy duties of matrimony. Katara and Aang clasped hands, remembering their own wedding day, but as they watched the bridegroom, their eyes were drawn to Sokka. He was… changing.
He remained in place, kneeling before a low table. But—it was like looking at him through water— he flickered, from a man to a scrawny teenager, and then years rolled forward over him. For a moment he remained at his proper age, but only a moment. Grey threads multiplied in his hair, and he stooped to the form of an old man. And then the wave pulled back, and Sokka straightened until he was a teenager once more.
But no one else—least of all Sokka himself—acted like there was anything amiss. Sokka's hands may be twisted with arthritis, his eyes might blur with cataracts, but his grip remained steady, his gaze intense. "I will," he said.
Yue began her vows.
Aang's hand tightened on Katara's. Later, they would hold each other and find words for whatever bizarre spirit-sight this was. But in this instant, they would both bear witness.
Yue smiled through tears and said "I will."
They kissed, and for a moment the entire chamber dimmed, before the bride shone with light. In the light, Sokka's age steadied until he was again a young man just entering his prime.
"Alright, not bad," said the Rabbit. She was already getting out a ball of yarn the color of blueberry tea, and two crochet needles. "I present to you the Moon Spirit and her husband, or Yue and Sokka for human purposes."
Katara clapped her hands in a steady rhythm, and she and Aang began to sing. Around the hall, spirits rattled beads or pounded hand-drums to make a joyful noise.
Katara sang, "The new house stands under the larch,
"The newlyweds enter hand-in-hand.
"And the hearth fire is kindled!
"Welcome home, welcome home,
Welcome home to each other!"
The song ended with a flourish, and Yue and Sokka got to their feet. Sokka whispered a suggestion in Yue's ear, and she nodded enthusiastically, whereupon Sokka swept her into his arms and carried her, both laughing, through the chamber, and into the hall beyond.
Katara and Aang were next to rise, and followed the bridegroom in a rather more modest fashion. As the Spirits great and small got up and moved to the dining hall, they chattered among one another:
"The Moon always lays a good table, you know. Do you think they'll serve poached peaches?"
"You know, I think it was a nice ceremony. It's a shame the groom is, ah…"
"Mortal?"
"I thought we were calling them 'time-locked beings,' it's more polite, I heard…"
Eventually, only the Ocean remained in the room's center, and the Rabbit, crocheting away.
"You did very well," the Rabbit said to the Ocean.
The Ocean grunted as he got to his feet.
The Rabbit added, "I thought we were going to have an unwelcome visitor, but it looks like Wan Shi Tong has decided to stay home." She tucked her crochet needles into the ball of yarn, evidently preparing to go in, to the feast.
"What are you crocheting for?" the Ocean asked her. "Even at a time like this?"
"Well, the need for dreams is constant," said the Rabbit. "And I thought, a Spirit and a mortal wedding, that's a once-in-a-century event. Someone ought to capture the moment. Send it as a gift to some sleepy child."
"There won't be children," the Ocean said in a low rumble. He sounded adrift under his bluster. A little sad.
"Well. Someone will find this interesting," said the Rabbit. Then she looked at the Ocean and set out a paw. "Shall we go in, old friend?" she asked, and the Ocean smiled reluctantly and linked his arm through hers. Together they entered the hall, last of the wedding guests.