* Do you wanna have a bad time?

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Acidtale tells the story of how a computer named Cypress destroyed the world.


Everything in the underground was very well. Frisk and Chara were staying at the castle with Toriel and Asgore (who had gotten back together), Alphys, Undyne, Sans, and Papyrus were normal, and Flowey had used the power of the souls to forever change him to Asriel. Then, Alphys built a robot. A companion to Mettaton. His name was Cypress. However, he was a huge control freak. So Alphys had to shut him down. However, he shot a special liquid out of his cables at the last moment to preserve himself. It hit Alphys. A couple days later, Undyne went to see Alphys because she hadn't been seen for a few days. Undyne opened the door and saw The Amalgamates and Alphys tearing up the place and going crazy. She looked closer. They all had pure dark blue eyes with no pupils and were oozing yellow liquid out of their eyes and sweating off their hands, paws, and claws. She saw them stare at her and attack. Now, the door was open. Undyne, Alphys, and The Amalgamates, all infected, stormed out. They attacked everyone and the infection spread like wildfire. At this time, Sans, Papyrus, and Monster Kid were having a sleepover at Frisk, Chara, Toriel, Asgore, and Asriel's house. All 8 of them saw the infection on the news. One moment, Mettaton was broadcasting about the danger of the virus, which had been named "Acid". Then, crashing was heard, Mettaton was heard screaming, and the broadcast went blank. A moment later, it came back on with Mettaton. Only, she had some of the lower colored panels on her ripped off, all the panels glowing dark blue, and yellow liquid oozing out of the holes. She, in a monochrome voice, told the viewers to get infected. She then said "Burgerpants, say bye!". Burgerpants was then heard in a monochrome voice saying bye. Then an ad for Nice Cream Guy came on with him infected and the TV service ended there. Banging on the front door suddenly started and the group closed, locked, and reinforced all doors and windows in the castle. They then drag their stuff to the very top floor of the tallest tower and barricade themselves in. Everyone is freaking out and it doesn't help that they can see an angry mob (including, Mettaton, Burgerpants, Nice Cream Guy, Undyne, Lesser Dog, Greater Dog, The Amalgamates, Alphys, Grillby, Muffet, Temmie And others) outside. A few days pass completely fine. However, their supplies runs low. Toriel and Asgore tell the others not to open or answer to knocking or the doorbell and then leave for supplies. They don't come back... uninfected. The remaining group tries to recount safety.

  1. Makes host talk in monochrome voice.
  2. Makes host leak yellow liquid from eyes, mouth, and hands.
  3. Makes host's eyes lose pupils and turn purely dark blue.
  4. Yellow liquid main way of infection spreading.
  5. Increases host intelligence.
  6. Makes host no longer need basic needs (food, liquid, bathroom, sleep, entertainment, and warmth).
  7. Makes host's number 1 desire to infect uninfected vessels.
  8. Very quick infection (infected vessel can infect uninfected vessel in matter of seconds).
  9. Able to infect anything with a soul.
  10. Host able to sense uninfected vessels.
  11. Unable to cross light gate into surface.

They becomes scared. They don't know what to do, they are running low of supplies, and it seems going out for supplies is impossible without getting infected. However, they find trash bags in the kitchen and make armor out of it. After equipping, the group runs outside and starts making progress towards the light gate to escape to the surface. However, they get ambushed. Infected Grillby unintentionally melts Papyrus's plastic trash bag. In a small spot, he is vulnerable. The infectants rush towards him to infect, but the group shields him. Endogony rushes forward and ends up getting a drop of yellow liquid on his bare bone. Since it is just a drop, every feels he should be ok. Getting closer, Papyrus starts slowing down. Suddenly, he screeches and charges at Sans. Sans dodges and catches a glimpse of his eyes. Oozing yellow liquid, and pure dark blue. The group starts running and almost makes it. Everyone except Monster Kid gets through because he almost trips. Frisk quickly runs and grabs him and together they make it through. However, Frisk and Monster Kid feel wierd. As they walk away, Frisk realizes what it is and rushes themselves and Monster Kid back to the gate. They jump through at the last moment as both their eyes turn dark blue and start oozing yellow liquid. All the infectants start banging on the gate. Suddenly, Napstablook floats through the ground because he is a ghost. However, he is infected! Due to this, the infection starts up on the surface and the light gate is finally destroyed. All the infectants merge together as one army and start ravaging the world. Meanwhile, Sans, Chara, and Asriel are hidden away in a secret bunker underground. They have a garden and a well so they can live indefinitely. They are also hidden and untouchable by the virus. Suddenly, a second Sans shows up. He explains that he is the canon Sans and that he came to help, however this universe is already a lost cause. Worse, the anamoly and the shattering of the space-time continium from 2 Sanses causes another Sans to be ripped from their universe and brought to this one. He is teleported into Snowdin and instantly infected. Eventually, the Tem Shop Temmie (named "Rachel") arrives at the bunker and explains her story. {Story: When Acid started up, she caught it on the news (the same news program the main group watched in the castle) on her TV (she had bought it with the extra money from college) in her shop. She then invited her family in and locked them in her shop. After a while, she heard other Temmies knocking on the door and in a monochrome voice asking to come in. However, everytime she said no. The other Temmies became restless and eventually got in at night and infected her family and would have infected her if she hadn't escaped out the emergency cat flap. Rachel packed a few things and ran for her life. She started wandering atop the trees to avoid infectants. eventually, she made it to the light gate and went through, she was a wandering Temmie on the surface until she came upon the main group}. The remaining group, now with Rachel and Canon Sans (who's portal gun's hyperfusion overdrive bulb calculator burned out and thus is stuck in Acidtale forever unless he can get replacement parts, which are only in the Lab universe) are left to survive in the bunker. Everywhere else, the world is a charred barren war-struck deserted wasteland. Surface, underground, it doesn't matter. Everywhere is just a charred barren war-struck deserted wasteland where many infected humans and infected monsters are roaming.

 Gaster, His Followers, and Annoying Dog


Due to the anomaly making Gaster never exist and making his components into Alphys, Sans, and Papyrus, he is completely fine and untouchable, beyond our world. However, if he wanted to return to normal into the universe, the anomaly would make him instantly infected due to 2 of his 3 component entities being infected.

His Followers

Due to the anomaly making them never exist along with Gaster, they were untouched too. However, they are much less powerful than Gaster and are unable to return to our real plane of dimension.

Annoying Dog

Due to his strong control over existence, he tried to stop the virus. However, he failed because Acid's power overpowers his powers. He was eventually forced to go into hiding with Gaster and His Followers. but at any time, he could return with no problems.

If Other Universes Collided


ERRORSans once tried to mix Acid with The Hunger. The chemical concoction was disasterious. The entire Lab universe everyone had been using for multipurposes had to be evacuated and a new Lab universe was needed. If Acid and The Hunger mix, a fusion of the two that has been named Xid (Ex-Id) would be made. Xid is horrifyingly blood-curlingly dangerous and if allowed to spread across the universes, would destroy EVERYTHING IN EXISTENCE AND THAT EVER DID EXIST and everyone would be infected, including Gaster, Annoying Dog, and Gaster's Followers.


Very much would change due to Acid overpowering zombie virus. It would make the zombies act like normal Acid infected hosts.


Very much would change because while infectants do whatever it takes to infect, generally effects of Acid are peace and calmness and the exact opposite of a crazy hyper party animal bouncing off the walls type.

Lab Universe

The universe would go on lockdown. The portal in and out would shut down, and the lab doors would lock. Some members might be infected, which would be a VERY big problem, however their intelligence should make sure everyone stays alive and evacuates safely to another universe and destroy the portal.

Underfell, Swapfell, & Flowerfell

Very much would change because while infectants do whatever it takes to infect, generally effects of Acid are peace and calmness and the exact opposite of a crazy hyper party animal bouncing off the walls type.