A/N: Here's some canon!Twelve/Clara thrown into the mix! Enjoy!

"Sideways in time" was how the Doctor put it. He and Clara had hit a clump of cosmic dust while in the time vortex and now they'd gone sideways. It was entirely possible, and he'd done it several times before, though never to a place that was so… so… placid. The planet was merely a dual-biome entity: water, and the very Earth-like forest the two were currently wandering in.

"Well, at least it's a change of pace not having to run around everywhere," Clara mentioned. With them having just escaped electromagnetic ghosts, calm and quiet was welcome for a change. "Where are we?"

"A planet that has no name, technically, and it looks like we only were bumped a few years off-course," the Doctor replied, looking about while waving around an absurd scanning device. It was positively huge, needing to be carried on his back and over his shoulders, making him look more like an aged Ghostbuster than an intergalactic stick insect. "You know, this presents us with a very interesting opportunity."

"…which is…?"

"If I can correctly calculate the space-time coordinates of this planet while we're here, when we go back to our dimension, we can see how much difference there is! Imagine knowing two possible outcomes of history! Normally people can only guesstimate using absurd conspiracy theories and probability equations riddled with organic error. This… this we can know for certain!"

Chuckling to herself, Clara only half-listened as the Doctor babbled on about the seldom-traversed field of dimension-hopping. He was absolutely overflowing in excitement, which was in no way fueling him onwards as they trekked further and further into the forest. She eventually told him she was going to sit down for a rest, which he took as the go-ahead to continue exploring without her. Taking out her mobile, she began to idly play a game as she took in the forest around her. It was even more peaceful without the Doctor prattling on, expertly identifying every plant and insect around them. That was part of the fun, of course, yet she still relished in the stillness of it all.

"Clara…!"

…and the moment was shattered.

"I'm right where you left me!" she shouted into the forest, not even glancing up from the device in her hands. She only looked away when she heard the Doctor's boots stomping through the underbrush, accompanied by high-pitched giggling of all things. Sure enough, two small children were attached to his legs, staring up at him adoringly.

"I thought you said we were alone on this planet," she quipped. The children then looked over at her, their wide brown eyes lighting up.

"Mummy!" they both cheered, running to her. Clara sat there frozen as the two attacked her with hugs. They couldn't have been much older than First or Second Year, dressed in matching jumpers, with the boy in trousers and the girl in a skirt and leggings. They had fluffy brown hair and the same mischievous smile on their faces.

"We found Da!" the girl laughed gaily. "Now we have to find you, Mummy!"

"Um… Doctor…? What's going on here?" Clara asked. Her own eyes went wide in confusion as she watched her space-beau whip out a scanner and begin analyzing the newcomers.

"They aren't anything I've come across before," the Doctor marveled. "Well, I have… once… sort of… though the genetic markers are completely off… and that doesn't even cover the ratio…"

"What's wrong, Daddy?" the boy wondered. He bounced over to the Doctor and stood on his tiptoes, attempting to see the device's readout. "Do you need to go back to Auntie Idris and fix it?"

Now that made both the adults stop and stare. There weren't many people who knew the TARDIS's name—that name, in particular—and this small child was well aware. The Doctor crouched down to be at eye-level with the boy, his brows furrowing.

"What did you say?"

"I… uh… asked if you needed to go back to Auntie Idris," the boy mumbled, his eyes immediately finding his feet. "Did I say something wrong, Daddy?"

"No you didn't," the Doctor replied. "Tell me: where did you last see us?"

"Umm… over there," the girl said, pointing into the wood. "Did you take a special way to get here?"

"No, I—" He was cut off by another voice in the forest, one that sounded suspiciously like his own.

"Alison? James? Where'd you go?"

"…Daddy…?" the boy marveled. He stared at the man next to him, peered into the wood, then back towards the man. "What's my middle name?"

"Huh?"

"What's my middle name?" James demanded with all the authority he could muster.

"Uh… John…?"

"DADDY! HELP!" the child screeched. The suddenness of the sound sent the Doctor toppling over onto his rear, and the boy was soon joined by his sister. Some leaves and shrubs rustled and before Clara knew it, there was a second Doctor rushing into the tiny clearing, scooping up the children in his arms.

"Who are you and what do you want with my children?!" the Other Doctor growled. "Why do you look like their mother and me?!"

"Doctor…? What's going on…?" Clara asked. She stared as her Doctor stood up and brushed off his trousers, the two men sizing one another up. "Is he this dimension's version of you?"

"He must be," the Doctor said. The Other Doctor placed the children down on the ground and cautiously walked up to his doppelganger. They stared at one another in amazement, mimicking movements and facial expressions, until they both burst into a maddening grin.

"Sideways in time!" they said in unison. The Doctors shook each other's hand, with the Other Doctor looking over his shoulder at the children. "James! Alison! It's me!"

"It's not you, Da!" Alison insisted. "You are you!"

"Yes, but this is an alternate me, from a different dimension," the Other Doctor explained. It was then that another Clara arrived, taking in the scene with caution. "Oh, good, Clara! Allow me to introduce you to you and me!"

"They're us…" Other Clara echoed.

"Admit it: that's not the weirdest thing that's happened," Clara replied. Her other self chuckled at that in agreement.

"Can't argue with that—come here, kids; Daddy and his other self are about to explain something terribly clever."

"Precisely, Clara!" the Other Doctor beamed. "This has happened to me several times in the past! Now it seems that thanks to the fortunate detour the TARDIS was able to provide, we've been presented a rare opportunity to compare and contrast our lives to this point!"

"Though really, it seems pretty much the same, aside from the going sideways bit," the Doctor mentioned. "I don't know what's in store for our future, though it seems like we have a bit of a sneak peek." He waggled his eyebrows and stuck out his tongue at the children, making them both giggle. "How the two of you managed this, I'd like to figure out. Perfectly spliced genetic coding is rare no matter what's happening."

"Do not turn my babies into experiments," the Other Clara warned. Clara stood and joined her adamantly—she hadn't birthed them yet, but that wouldn't stop her from protecting her children.

The women then fussed in a motherly fashion over the kids while their space-husbands decided to swap theories of this and that, completely ignoring the fact they were probably at risk of creating a paradox the longer they stood within proximity of one another. James and Alison, however, were confused, and figured it would be something that their parents could explain later on. There were plenty of things that they were told would make sense later, and the youngsters had learned to roll with it.

…because their not-mum was right: this wasn't the weirdest thing that had happened, and it wasn't going to be the last.

Later on, as the nigh-immortal Time Lord punched a diamond wall, one thought ran through his head, desperate, angry, protective, and unsaid as he mocked the being that was to bring him to his death:

Their names were Alison Joan and James Clark Oswald-Smith—the prophesized Hybrids—and now they would never exist in his dimension. If he couldn't have them, then no one would.