There were some things in life no one could predict. Like which element someone would choose in a game of "Earth, Water, Fire, Air" (the mathematics of probability never seemed to apply, especially when Sokka played), who Momo would steal lunch from next (for reasons similar to the previous situation), or when Toph would take her next bath.
They were just some of the unsolved mysteries of the world and, truthfully, they were what made life interesting.
However, there was interesting unpredictability, and there was nightmarish unpredictability.
Standing in the hole he had smashed in the wall, creating a tunnel from one chamber to the next, Aang stared at her in disbelief. Crystals that protruded from every surface of the cavern emitted a soft green light, one cluster in particular hanging over Katara and casting a sort of viridian spotlight around her.
At least, the person looked like Zuko. It was hard to tell with the Earth Kingdom clothes and grown out hair and, well, Katara was kind of obscuring most of his face.
By kissing him.
At the sound of his voice, the pair jumped apart as though electrified. Katara scratched the back of her neck, smiling nervously as her cheeks turning almost the same colour as Zuko's scar. Trying to sound casual, she said, "Oh, hey, Aang. I, uh, didn't expect to see you here."
"I came to save you!" he said, remembering his intent now that his would-be-lover and sworn enemy were clearly two separate people, and not some sort of twisted fusion. "Um. . . What are you guys doing? Together?"
"Healing," Zuko blurted in a strange-sounding voice. It took a moment for Aang to realize that it was because he wasn't yelling or threatening him and instead seemed almost . . . bashful? "She was trying to heal me."
Beside Aang, Iroh was grinning so widely it appeared as though his face might split in two. "Oh, prince Zuko, I knew you had it in you! Should I stay in the teashop tonight so you and your friend can have some privacy?"
"No!" he shouted, reddening to the tips of his ears. The familiarity of his anger helped reassure Aang that he hadn't stumbled into one of those alternate realities Sokka had been talking about, were up was down and the Air Nomads were genocidal war-mongers.
"So . . ." he said, gaze darting between the pair, still not quite able to make sense of the situation. "Is this the part where I save you, or . . . ?"
"Actually, we, uh, we've been talking and, um, w-we decided that, uh –"
"I've decided that I wanna join your group," Zuko finished for her, tone even and sure as he looked Aang straight in the eye. Then he did something that made Aang's collapsing brain deteriorate a little more; he reached out and grabbed Katara's hand, giving it a gentle, reassuring squeeze.
With a shout of congratulations ("You got a girlfriend and you've come to your senses!"), Iroh pulled a protesting Zuko into a fatherly embrace, leaving Katara to comfort Aang.
It was a wasted effort; no amount of explanation could mend the fact that his entire reality had been flipped upside down.
Crossover: To move from one side to the other.
Disclaimer: 'Avatar' and all of its contents belongs to Nickelodeon, and is no way my property.