Gaster was beginning to become afraid. He was keeping himself barely a step ahead of the Error, and he was slowly running out of energy. Before long, he would find himself unable to timeline-jump, and he shuddered to think what would happen when the omnicidal murderer finally caught up with him in this state. He realized that he had only one chance at survival- he had to find someone who did have the power necessary to defeat the Error... someone with similar interests to himself. Well, he supposed, that was simple. All he had to do was find any monster, from any alternate timeline. They were all threatened by the Error's machinations, so it should be simple enough for him to find someone to help him.
The only problem was, he knew that by some strange law of the universe, he was only able to carry one being at a time with him throughout the timelines.
Suddenly, he realized something. He had an epiphany, in a certain way of speaking. It came to him out of nowhere that perhaps, if he played his cards right, he could trick the system. What if he was only bringing one person with him... he would simply bring... several of the same person. That was the answer!
He waved his hand in front of his face and opened a portal to a random timeline. Stepping into it, he looked around, still not quite sure exactly what universe it was. The first thing that met his eye was Papyrus, leaning against a tree near an abandoned sentry station and smoking a cigarette.
Gaster cringed and backed into the shadows. He knew what was going to go down if Papyrus spotted him. Under normal circumstances, he would have immediately evacuated the timeline... but he remembered what the reports had said about this timeline's Sans. So he guessed the wheel of fortune had decided on who he would be bringing with him. Sans it was, then.
Apparently, the Sans from this universe had had some rather... close contact with the Error in the past. Somehow, he survived. This would make him useful. Gaster sidestepped the tall skeleton and went off in search of his brother.
Sans wasn't difficult to find, simply sitting in his house cooking spaghetti. Gaster decided not to waste time.
"Greetings, Sans."
Blue let out a loud 'YELP!' before turning to see who it was. He looked confused, but also excited at a possible new friend. He stopped his cooking, but completely ignored the still-on stove.
"Hi there! Who are you? I am the Magnificent Sans!"
The Error had a job to do. Perhaps not the average nine-to-five gig that most people are used to, but a job nonetheless. He sifted through timelines slowly, trying to locate his quarry.
Error stopped at a certain timeline. He mumbled something under his breath before looking through the Underswap code. He hated this one. An anomaly in the code, but it wasn't Gaster. Just...something that shouldn't exist. One being of course stopped him from erasing it in the first place, which is why he kept away from it at all times. But this was an exception.
"Hello. I am Doctor W. D. Gaster. I apologize for being hasty, but I must get straight to the point, I haven't much time. According to my sources, you have encountered the creature known as Error Sans in the past, have you not?"
"Error...Error..Er-ror...Oh!" Blue laughed, "Ya! I met him a long while ago. He actually seemed a bit lonely, stuck in that blank white space. Why? Also, do you mean Gaster the riverperson? You're a doctor?"
Error stopped in the code and nodded to himself, muttering about something or someone.
"Indeed. But... Well, I would be willing to wager that loneliness is not the reason that the Error is out for my blood- and yours. I... am afraid that I must request that you rapidly evacuate this timeline- with me. For you see, unless I get your help, I will not exist much longer. And if I do not leave here, then it is very possible that the Error will wreak havok in this timeline in his attempts to purge the world of myself."
"Wait a second? What? Whatever! I, the MAGNIFICENT Sans, will help you in whatever way possible! No matter the cost, I'm always willing to help!"
"Wonderful. Wait. Damn it, he's here! The Error is here!"
Gaster turned on his heel and fired an invisible pulse of energy out of his hand, blowing the skeletons' door off of it's hinges and forcing Error! Sans to take a step back, before grabbing Swap! Sans and dissapearing into thin air.
The Error cursed and dissipated in a flash of ERRORs.
Meanwhile, Blue huddled, terrified, beside Gaster as the hurtled through the timelines.
"Hey! Where are we going?"
"I'm afraid I don't know, exactly. I panicked a bit. All I know is that we will almost definitely arrive in a timeline vastly different from yours, and one with another Sans."
The two of them suddenly hit the ground hard, rolling forward a bit.
"Speaking of that, this is going to get confusing fast. What can I call you, other than Sans?"
"My friends call me Blue."
"Wonderful. Well Blue, you see, one day, we will all be consumed by the Error, perhaps even you. So I have decided to gain the advantage preemptively. Instead of allowing him to eliminate us one by one, we shall band together and fight him all at once. Then, perhaps, we will succeed in ki- capturing him for good."
"Wow! That... sounds complicated. But we're going to band the entire Underground together!"
"Not just the Underground, my friend. Let me try to explain. When someone is determined enough, then they have the capacity to alter time, to go back to a time before a given bad event happened, or just to live through something again. But when they do so, the timeline isn't exactly the same. It changes. And the old timeline is left floating through space as if nothing happened. With dozens of beings throughout all of time doing this over and over, things began to get stranger and stranger. Eventually, certain timelines barely resembled the original. Thanks to a fortunate accident on my part, I am able to travel through the timelines- hence the Error's insane hunting of me."
Error! Sans finally got a lead on the position of Swap! Sans and Gaster. He began shifting through the timelines, trying to reach them, before he sensed some sort of disturbance. He got sidetracked, and started moving away from his primary target, heading instead for yet another timeline.
"So, everything resets until nothing is the same?"
"Essentially. Small changes can eventually build up. Either way, this is quite a curious timeline. If I recall correctly, this one is actually a few thousand years older than yours. We're not just in an alternate universe. We're also in the future."
"Really?"
"Indee-"
Gaster suddenly cringed.
"Damn it all to hell. I feel yet another disturbance. Like the Error, but somehow... cleaner, more distinct.
He looked over at an obviously confused Blueberry.
"Never mind. I'm just rambling to myself."
In another timeline, a smol, emo-hair styled scientist rushed around his lab. A machine, capable of timeline jumping, was malfunctioning. It was picking something up-an error, of sorts.
"Nononononononono!"
The scientist, looking like a strange, lab-coat wearing combination of Sans and Mettaton, furiously tapped a button on his machine, trying to get it to stop spewing smoke. His voice was feminine, superficially resembling that of Alphys. Finally, the smoke cleared, and he could somehow see through the machine's "door." On the other side, he caught sight of a being that nearly made him faint. He saw Error! Sans. Headed straight his way.
(Appearance link here- /9xZnBfF)
"Oh no. The disturbance is growing."
Gaster set off toward the Judgement Hall, from which he could hear loud booming sounds, and feel heavy vibrations.
Blue followed after Gaster, confused. He still went along with it.
"The Error is nearing this timeline. We must hurry."
Gaster rushed forward with Swap! Sans, reaching the Judgement Hall in a hurry.
When he stepped into the area, he took a step back in suprise.
Frisk and Sans were fighting, as he had expected, but they looked most unique. Gaster realized that this shouldn't seem strange; it had been 6000 years. Sans silently flicked his finger back and forth, firing bones at the human, who dodged effortlessly again and again. They reached Sans and slashed with their worn knife, but Sans dodged easily himself. He noticed Gaster and Blue, but ignored them.
This Sans' appearance very closely resembled that of the "original," but with a much more weathered appearance.
(Appearance link here- /7GiohgX)
Blue stepped back as well. He stared directly at him and Frisk.
"Who...who are they?" Having seen only a Chara in his timeline and never a Frisk, this was confusing. It was also confusing since there was another version of Sans just right in front of him.
"Aha. Well, obviously, the skeleton is you. Simply... older. And quite a bit more serious. Oh. And that is Frisk. I have absolutely no idea how they are still alive, and even less idea of how they are still a child."
He took a step closer to After! Sans.
"But one thing is for sure... your alternate self is indeed very powerful. Wait."
Gaster paused.
"Another Sans is in danger. I believe it is the Error's doing. We have to reach him."
Gaster put one hand on Blue's skull, and then sent another flying off to After! Sans, whom it stuck to.
"Let's go, gentlemen."
Gaster, After! Sans, and Blue all disappeared in a flash of black energy.
The Human was cardinally confused.
The science-minded Sans, known informally as Dr. Grape, couldn't help staggering a few feet closer to his machine to get a better look at the Error. Unfortunately for him, high-heels were even worse for balance then they were for lab work, and he tripped forward, flying into the machine and landing right next to the Error.
"W͚̱̞͚̻͚͙͞ha̢̩̗̼t͚̤̗̕ ̸̙̞̯̤̗̣t̯̩̭̬̰͕͔h̴̭͕̙è̻̻̖̝?͏̖̹̲̗͇͚͉?" Error stared at Grape and groaned. He pulled the scientist and his SOUL up with lines of blue, and held him there.
"A͚͍̙̬̠͖͝n͞ḏ̘͇̪̬͠ ̫̥̲͉w̡͔̥̟h̵͎ó̰̼͈͙ ͔͍͘a̫ŗ̺̠͕̟e̴ ̨̖͇͓͚y̯͚̲o̵̬̟̣͕̠̤ͅù̱͙?̫͓̟̞͚"
Grape's breathing became fast and raspy. "Uh...I c-c-could tell you, b-but...I'm in a bit of a bine. Hehe..."
He laughed at his own joke, and adjusted his glasses.
"M-my name's Sans. M-m-m-my friends ca-call me Doctor Grape, though, because my favorite food and hair color."
"W-what's your na-na-name?"
Error didn't laugh. He tightened the strings that surrounded Grape's SOUL.
E͉͔̟͓̬͠r͓̞͓͎̹͟r͍̱͎̝͠o̘͚͉̹̰͇͢r̮̗ ̕S̛a̘ns҉̱̼̱͎͍ͅ.̧͓̩̦͎͙̼͈
"Uhuh...c-cool, I-I gu-guess...?"
Grape shifted nervously.
"Umm...I'll b-b-be on m-my way now!"
Grape backed away. trying to walk back the way he came. However, he forgot about the strings. He cried out in pain, and clenched his chest.
"H-h-h-h-h-h-h-hey! Lemme go!" he said, dropping his clipboard.
Blue was just as confused as the human, but looked at After! Sans.
"Hi there!"
"who are you and where am i and when can i get back to killing the human"
"Greetings. I am Dr. W. D. Gaster, and this is Sans, but from a different timeline than you, of course. I'm afraid you and I, as well as every being in the universe, is currently in grave danger."
"well i have my own timeline to protect so i'm leaving"
"God, it is hard to make out what you are saying, Sans. Actually, I'll call you Grey. Can I call you Grey? And are you incapable of putting damn pauses into your speech?"
Grey clenched his fist. His eye hadn't stopped spewing flame for an instant. It wasn't about to, either.
At approximately that moment, Blue, Gaster, and After! Sans burst out of a portal and landed in front of the Error.
Gaster smiled. He waved his hands, summoned up ethereal shapes, changed his facial expression, and made multiple hand movements, trying to approximate wingdings.
Translated, he had said something like- YOU'RE NOT THE ONLY ONE WHO CAN USE CREEPY FONTS, ASSHOLE.
Suddenly, without even noticing Gaster, Error! Sans disappeared with Grape. He had teleported away, but couldn't move too far unless he wanted to risk letting go of Grape. He was only a few hundred yards away.
"Afra̶id I̸ ́ca͏n̸'͘t ̵d̶o th͞at.͏ You̢ ͏see, ͠i'm̕ ̡t͞ry҉in͝g̡ ͡t̶o̧ ͡f͡i̧nd ҉a͡noth̕e͟ŕ be͡i̶n̸g͡,̀ G͟a̕ste̵r. B̡ut ̶f͘ŗom ͠w͝h̵at̡ i'v̸e s̕ęen̛,͏ h͜e͠'s̀ ţryin̷g͏ ͝to͜ r̀o͡u̢n̵d̕ ͡u҉p̶ e̡a͘ch Sa҉n͏ś. Ì c͢an't͜ l̸e͡t him̀ ̴g̢ęt͘ y̴ou̸,͝ so̧ ̷y͢ou͜'r͢e ͜c͜ǫm̢i͠n͝g̵ ̴ẃit͝h ͜me҉."
Gaster groaned.
"Damn it! It's hard to talk like that!"
Blue turned to Grey.
"Hey! I'm Sans, but you can call me Grey. Nice to meet you!"
"... eh there's no one to save in my timeline anyway... so i'll put up with your shit for now"
The Error turned, noticing the three beings following him, and practically licked his lips.
He didn't even need to find them.
They had found him.