If he was going to miss anything, anything at all, it would probably be two things: Happy Hour at Grillby'z and the fact that he wouldn't ever get closer to remembering all the things that he had lost, which was really the only other thing that he actually wanted to expend effort achieving. But those things weren't worth everything else that they were packaged up in, that was for sure.

If he was going to miss any people after doing this, and if he really thought about it, it would probably be only two people: the old lady that he often talked to from behind the door to the Ruins, and that kid that gave him a laugh every now and then wandering through this dangerous Underground. Just those two.

But he would see them again, so that wasn't a huge deal even if it did make him hesitate the slightest bit. He would see them again very soon, even if they wouldn't be quite the same as the ones from his memory. Even if he wasn't going to be the same as they remembered, either-although he would do his best, for whatever weak measurement that was.

For the first time, his heart wasn't racing because he was afraid, but because he was excited, the glow of the machine lighting up his face.

This was it. He wouldn't continue to sneak away to the shed and just watch anymore. Today was the day he actually did something about it, actually did something about something for once in his life. He'd been taking notes on it all this time; beside him he had a book full of them that he flipped through for a second, reconfirming his calculations.

Then, tearing off a piece of the notepaper and a piece of tape, he punched in the coordinates for the machine. Then he stepped inside, and as he heard the whirring of the engine coming to life he quickly, clumsily, set the timer for the explosives on the inside of the booth and on the engine. They would give him plenty of time, at least two hours unless he, on his second trip, set them to blow sooner.

With everything in place, he disappeared.

There was a distortion, the kind that no one would notice except for someone whose job it was to look for it. And no one was really assigned to a job like that, so it went completely unnoticed by everyone. The sky dipped into rainy weather for a couple minutes and then went back to sunny, and that was all that the weather was willing to do to acknowledge that something was different and wrong today.

A second distortion occurred in the world, and with it the clouds returned but this time they had no rain to give. After that, the source was still around even when the glitch in the coding was mended. A small skeleton was checking himself over in a messy room, one that was only a little less filthy than his own.

Everything here was just as he had seen it in the viewer on the machine, further assuring him that he was in the right place. He held, grasped tightly in his sharp clawlike hands, a blue hoodie that he experimentally put on. It fit perfectly, although it smelled like it hadn't been washed in hundreds of years. There were hot dogs in the pockets, which he started to absently munch as he sat down and thought. Judging by the light streaming through the window, it was already late in the afternoon. That meant that his other self had been sleeping way into the day, which was bizarre to think about. Should he come out of the room? Should he stay in until nighttime? And what was that water that fell down past his window earlier?

Maybe it would be better to make the decision after affecting a few cosmetic fixes. He couldn't change everything, but at least he could make his differences a little less... noticeable, to those who weren't making it their business to notice. After that, he'd decide if he wanted to have a good rest or go out and explore the house.

His heart was still beating hard. If only because he hadn't expected it to go so well as it had. It was surreal. It was like he knew it wouldn't last.

But it would. He had seen to that.

Sans groaned. For some reason, his head hurt a lot more than usual when waking up. Maybe it was because he had been woken up by a small series of crashing and scraping sounds, or maybe it was because he had woken up lying on a hardwood floor rather than his usual mattress. Immediately he knew that something was very wrong, something had happened in the early morning that was just outside the range of his memory. The aching in his head only got worse with that realization. So with a little bit more effort than he wanted to give, he pushed himself off the floor and into a sitting position.

There was a piece of paper taped to his forehead, which flopped in front of his eyes as he came upright. "?"

Reaching up, Sans tore the piece away and then realized that the tape, which had held it there, was still stuck on his skull. He gave an irritated grunt as he scrabbled to pry it off, succeeding only after making several painful scratches against his throbbing head. That was over with. If this was Papyrus telling him to take out the garbage again... But then he looked over the note, the corners of the grin usually frozen on his face slowly moving down until his expression looked like a grimace instead.

Then, when his eyes had finished their cursory glance over the note's contents, he turned around where he sat and looked at his surroundings a little closer. They were familiar, and yet at the same time not. It was what looked like a dingy shed with only a couple working lights, the floor bare and the space almost empty of anything but a table and drawers stuffed to bursting with papers.

Well that wasn't entirely true. The room had that table and drawers, and it also had a rusted machine that was set in the corner. It was tall and resembled a booth, with a set of controls on the side of it, but the booth and the engine next to it looked like it had been made with junk. Of course, that assessment might be because it was crumbling and obviously broken, the engine busted and the booth collapsing in on itself. From the way the metal was softly groaning, Sans could tell that it had been destroyed recently. Very recently.

The noise that had woken him up, perhaps.

He glanced down at the note, looking it over for a second time. He couldn't comprehend it. He knew enough to understand, but at the same time everything was registering so slowly, more slowly than usual. And outside he could hear disturbing noises, like someone screaming in the distance, that occupied his attention for a moment before returning to reality.

Scrawled on the notepaper, in messy handwriting and with the texture of someone using a wall for a hard surface, was:

hey there shitstack,

I don't really know if you'll know who and what i am. I got my machine working, but from the looks of things you never did the same for yours. weird, huh? works out fine for me, though. also, thanks for doing me the favor of being asleep when i dropped by. all i needed was a little bit of medicine to keep you knocked out. hope I didn't accidentally kill you, but if i did you wouldn't be reading this so uh.

I could have just left you here now that the machine is destroyed, but i guess since you're me in another world I owe you at least an explanation. the short of it is that i'm sick of this place. hang around here for a while, you'll see what i mean. and your world, or at least what i've seen of it, looks a hell of a lot easier than mine. so I decided that we're trading places. forever.

sorry buddy. but don't say i didn't do anything nice for ya. i left one of my coats and shoes there for you to wear, because you're gonna get pulverized if you walk out in pink slippers, loser. and in my room i left a list of things that you're going to need to know about this world if you want to survive-couldn't include it here since I'm running short on time. but i'm sure you know where my room is. it's a lot like yours. don't get caught by papyrus when you go up and get it, though. he's always got a bone to pick with us.

i'm sure you'll do fine.

Sans.

Author's Note: Welp, I ended up having the muse to make a contribution to the "Sans/Papyrus/etc. swaps places with their Underfell counterpart" genre. I hope that you enjoy my interpretations of both Undertale's Pacifist Run and Underfell's Pacifist Run!

Next Chapter: Kid Gloves