A/N: Okay so about 100 years ago, I mentioned a space au based around Earth's Last Stand. And it's so dumb but I love it, and I want you all to know that this was pretty much inevitable

1. building houses in the spaces left behind

"I can't believe I'm sitting in space jail with you of all people," Raph snarks, mainly just to fill the silence that's fallen between them – but it's the wrong thing to say when Mike lifts his head, and a bright smile fills his face like a slant of sunlight, at the same time the content powder blue of his winding full-body tattoos churn gray against his green skin.

Raph seems to have that effect on him lately. In another time, he and Mike were close; but in another time, Leo was the leader, and Raph can hardly imagine that. Memories of the 'prime timeline,' as Don calls it, the timeline they were splintered from, are faded and vague and faceless, and all Raph knows with any clarity is that he is much different from the Raphael that saved Earth alongside his brothers.

For one thing, he can't seem to say two words to Mike without hurting him somehow. And he doesn't mean to, doesn't want to, and this isn't the way it should be. They're supposed to be close, that's just how it's supposed to be. But they're their own people now, the Professor has explained, and they have to build their own memories and relationships. Clinging to the cloth they were cut from won't do them any good, because they don't belong to the fabric of that time anymore. Not since their Other Selves returned home from the past or the future or wherever they went that gave Raph the opportunity to exist in the first place.

Mike's good humor is largely convincing as he says, "Technically this is just a holding cell. We weren't really arrested. And Le' didn't mean to start a mob," he adds, as though he can't help defending Leo while Leo isn't here to do it himself, "he just gets really excited about cartoons, you know how he is. How was he supposed to know the artform is practically a religion on this planet?" His eyes move away, watching the other detainees with interest, and he adds, "Sorry you're stuck here with me, though. We'll get out soon."

(Raph thinks he remembers fifteen years spent isolated underground. He can't imagine living those years, not when the Professor takes them to brand new planets all the time and gives them whole days to play and explore, and cleared out a big room in the galley for all of their found treasures. Raph thinks he would suffocate if he had to spend even one day hidden away in a sewer.)

The cell door swings open, and they look up in time to watch Don and the Professor rush in. Leo and April are hot on their heels, which means Casey is manning the cruiser outside, and Raph can only imagine how well that will end. But he's happy to see April, smiling automatically at the way she shoves past an alien twice her size to get to Raph; and similarly, Mike is laughing at the goofy way Leo is draped over him, all arms and apologies and 'are-you-okay's.

If anyone could be considered Raph's best friend, it would be April. She's listened to him wax almost poetic about his secret crush on Casey, and with zero judgement; which is fair, considering the sappy way she talks about their brainy leader. April is Raph's first pick, the same way he's her's – the way Casey is Don's, and Mike is Leo's. This wasn't the way of things before, Raph is pretty sure, but it's what he knows, and he wouldn't change it for the cosmos.

Don is cupping Mike's blank cheek in exhausted relief, and reaches for Raph the same way a moment later, grinning in a way that shows off the gap in his teeth.

"We're fine," Raph tells him, and looks up at the Professor as he approaches, adding, "Promise." And once upon a time, Raph's father was a tall rat with kind eyes, but now the closest thing to dad that Raph knows is the android that leans over to encompass them all at once in his long noodle arms. There's a bomb in the Professor's chassis, and in another place he died to save them all, and Raph closes his eyes and leans against the packed warmth of that hidden fusion core and is glad to be alive now instead of then.

"Let's go home," the Professor says cheerfully, squeezing them tightly before letting them go. Raph hops to his feet agreeably and follows his family through the cell door. Mike's tattoos are a happy, swimming coral as he marches hand-in-hand with Leo, their joined arms swinging, and he catches Raph's eye for the briefest of moments while the security guard by the exit checks them out.

"Told you we'd be out of there in no time," he says, ever the peace-keeper, and Raph knows that he will always be forgiven those tiny, inconsequential moments of hurt for as long as he lives.

But he doesn't want to hurt his brothers – especially not Mike, of all people, who is steady and patient and grounding; who acts as their family's unspoken diplomat those numerous times they stumble unwittingly into hostile territory; and soothes Leo back from those countless confusing, frightening dreams of fighting and falling; and reads familiar stories for his siblings out of ancient books of incomprehensible text for hours on end, on those nights when space feels too deep and too dark.

Mike reminds Raph the most of Splinter, when hardly anything else does, and Raph desperately wants not to disappoint him. So he nudges Mike's shoulder amicably, and watches the inked patterns there spin into hopeful yellow, and says, "Could've been worse. Could've been stuck there with Casey."

And it's not much, but it's enough to make Mike tip his head back and laugh – and Raph knows that beginnings have been built on much worse things than a handful of simple joy. He's happy to start from here.

(There's a pit in his heart full of a love that can't be touched or changed, fierce and unrelenting and far older than the fracture of a timeline Raph exists in. It startles him sometimes, to realize the bone-deep degree of that devotion, and he wishes he could remember what put it there. And he doesn't know Mike the way he knew him in another world, but he knows with absolute certainty that there is nothing in the universe Raph wouldn't do for him. And most of the time, knowing that is enough.)