Like most of Sans' shortcuts, this one left him dizzy. Feeling a little sick. It used to be easier for him to do a shortcut, but since he'd been forcing himself to practice more often, it had gotten harder and harder. But at least he'd left that blue guy behind. Sans just knew if someone saw the clone, they'd kill it and then come after him. It was an affront to both Sans and Papyrus for that blue thing to exist, especially when they'd worked so hard to get a safe house and Paps a job in the royal guard.

Leaning against the wall of the shed outside of their Snowdin house, Sans decided that the most likely culprit was Alphys. She was supposed to be working with determination, but given her twisted sense of science there was a chance she could have gotten her claws on a bone sample from him. After all, he fought plenty. There was lots of places she could have found a chip or two.

Right now, Sans needed a nap. But he couldn't nap, because today he wasn't supposed to nap and he'd already broken one of his personal rules. Couldn't hand the bad times from that any more. Maybe he could get a hot cat, but that was optional. He'd already left his post, having fallen asleep, and with the looming threat of a blue puffball on the horizon... Sans figured if he was given a shit dime, he'd be in for the whole shitty dollar.

He reached into his pocket, flipped his phone open... and just stared at it as he made his way up the stairs to his room, avoiding the carefully staged Sock War that his brother had set up to demonstrate attack plans should their house ever come under siege. Paps' sock was a christmas stocking. Sans' was half a red sock with a ripped toe. The rest of the monsters were tube socks.

Sans really hated tube socks. Assuming the blue guy stuck around, they'd have to add another one to Paps' little war game.

His clawed fingertips traced over the one on his phone. Why was he having such a hard time making this decision? Either he told Paps about the faker or he didn't. Either way he was going to have a great time dealing with the inevitable aftermath. It would probably involve food, bandages, and dusting an annoying monster with a huge mouth. ...man, did killing your own clone count as homicide, or suicide?

Sans didn't know. He flipped his phone shut and traded it for his door key, which was unceremoniously shoved into the knob and turned to reveal-

Sans' room. Just how he left it, really.

Except it was clean. Which wasn't how he left it at all. All of his trash (the kind that didn't have important notes on it) was piled neatly in the corner. There was a rope around the trash cyclone's neck, which was keeping it happily contained to stirring up said corner-trash pile. His mattress had been shoved back up against the wall, and his own collection of socks and extra clothes had been designated their own space at the foot of it. What was probably the weirdest was that all of his Quantum Joke books, volumes 1 through 3, Extra Dark Matter Humor editions were neatly on display on what Sans could only call... a desk? It was really just a board on top of some more of the junk in his room.

Sans hadn't looked at a Quantum Joke book in years. They had been shoved under his bed and forgotten as soon as Paps got into the guard and he got assigned to be a sentry.

"What do you call an apathetic mass," Sans read, taking one down and opening it. "Doesn't matter."

The blue clone had been here already. And he'd dug around in Sans' stuff, which was worse.

Sans heard a door slam. He jumped and the joke book fell to the ground, opening to a new page, a new joke. What do you call a guy on a slope helically wrapped around an axis?

Screwed. Sans was so screwed.

Paps was home (could be home, some rational part of his brain tried to argue) and some stranger had obviously been in their house, because Sans would never clean his room. He just didn't have the energy after working three jobs and still making time to train with his brother. They'd have to change out the locks, Paps would have to fight with him in public to reinforce the idea that he was a complete hardass that nobody should stand up against, and Sans would get extra shifts. No more extra training for him.

There was no reason to panic, but Sans was doing it anyway. Quietly.

Sans rushed out, not bothering to lock the door as he took a shortcut into the kitchen, sidling up against the wall. He tried not to breathe loudly, but even short shortcuts could leave him out of breath. Sweat slipped down his skull. His red eye flickered until he made it blaze again.

Sans had to go face the music.

He took a deep breath and walked out into the living room, a 'Hey, Paps' on the tip of his tongue when he saw it again.

The blue clone.

And it was PICKING UP THE SOCK WAR.

Sans didn't even realize he'd taken a shortcut until he slammed into the other, a fresh bone pressed like a knife against the clone's neck. More sweat poured off of him. It came back here. That meant that it had some way to get in. It had done it at least twice, assuming the damn thing hadn't just taken a shortcut to get inside in the first place.

"HEY," the clone complained. Sans ignored him, ready to dust. "IS THAT ANY WAY TO TREAT THE AMAZING COOK, SANS?"

...cook?

All it took was a moment's hesitation. Confusion. As soon as his bone wasn't close enough to kill, the blue faker grabbed waist, spun, and suplexed him.

The impact left his skull rattling. What the hell? What the actual hell?

"CAPTAIN ALPHYS TAUGHT ME THAT," the blue faker said proudly. Sans remained on the floor. "I DECIDED THAT WE SHOULD BE FRIENDS, AND THE BEST WAY TO MAKE FRIENDS IS TO SHOW THEM YOUR PASSION!"

Sounded like Undyne, to Sans. But the faker had just mentioned Alphys. Alphys being a captain? Had she been promoted to something else by the king, commissioned to make this obscenely happy... thing? How could a clone of him EVER be this cheerful?!

"SO, TRAINING! CHECK," The clone said, making a little check mark in the air. "ORGANIZING THINGS! CHECK. I THINK YOU'LL BE VERY HAPPY WITH YOUR ROOM WHENEVER YOU SEE IT NEXT. AND COOKING!" The blue thing paused, looking sheepish. "...NOT QUITE CHECK. BUT REST ASSURED, I'M GOING TO MAKE THE BEST MAC AND CHEESE YOU'VE EVER TASTED, OR I'M NOT THE MAGNIFICENT AND BOLD SANS!"

Oh, hell.

Sans' skull really... really hurt. "fuck," he mumbled. The room was spinning. Hadn't done that since the last time Sans had overdone it training. Which was yesterday. He'd ended up fainting yesterday. Paps'd yelled at him, n' then he'd fallen asleep this morning...

"YOU REALLY SHOULD WORK ON THAT BAD HABIT," his clone admonished him. "WHAT IF KIDS WERE READING THIS?"

What was he even talking about.

"what the fuck," Sans concluded. He barely noticed the grocery bags spilling out onto the floor. The blue guy must've dropped them. He had just ditched the clone- when had he gotten a chance to buy any?

And then he passed out.

I guess I'm writing more of this? It's honestly pretty fun. Underfell was created originally by the underfell blog on tumblr, and underswap was created by popcornpr1nce over there, too. This story is just my interpretation of ideas for some fun. Thanks for reading!