1 - 20 of 4,263 Works in Alternate Universe - Underfell (Undertale)

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  1. Tags
    Summary

    The first time it happened you thought it had been a fluke: you’d gone to bed Tuesday night and when you woke it was…Tuesday morning? After the second time you realize something is very, very wrong.
    The cycle continues for months, but just when you’ve all but forgotten what hope feels like, something unexpected happens: Monsters emerge from beneath Mt.Ebott and time begins again as if it never stopped in the first place.

    Barely holding yourself together, you find yourself the servant of lieutenant Papyrus and his brother Sans.

    Language:
    English
    Words:
    10,399
    Chapters:
    3/30
    Comments:
    13
    Kudos:
    36
    Bookmarks:
    9
    Hits:
    213
  2. Tags
    Summary

    When monsters and humans went to war, the monsters were sealed underground by seven of the most powerful human magicians. Though they wanted to fight back, they lacked the power to do so. The underground has suffered in recent years after the Dreemurr family lost their children. Monsters are starving, violence is common outside of settlements, and the king seldom leaves his throne room. A new human child has fallen underground. They are the 8th human to fall, and the 7th soul to be added to the king's collection. But a certain flower hopes to change their fate...

    Language:
    English
    Words:
    4,367
    Chapters:
    1/?
    Comments:
    2
    Kudos:
    1
    Hits:
    12
  3. Tags
    Summary

    “It's late, and it's raining,” you state, tugging his sleeve and halting his steps. The smell of smoke is strong, and it mixes with the earthy scent of the night. “Why are you trying to sneak away? You know you can stay for as long as you'd like.”

    He turns around, his figure darkened by the poor lighting of the patio, plus the lack of a moon.

    “solid suggestion, but you and i both know that's not a good idea anymore,” he replies, his voice sounding on the edge of exhaustion.

    Far used to his behaviour – one you've been a witness and victim of for the past few months – you roll your eyes and fetch a candle and a match from your pockets.

    “Oh, please. Don't be silly! You're always welcome here.”

    And as the flickering flame brings about clarity into the deep darkness of the garden, you quickly draw back a comment on him being dramatic.

    He's covered in dirt, and the injured body of a familiar face lays motionless on the floor.

    “just to let you know," he says, chuckling, ”i was only gonna drop this off." He gestures at a small, black box he retrieves from under his suit. "but that was your last chance to reject me, so now the fault's on you, if ya didn't want this.”

    Language:
    English
    Words:
    11,088
    Chapters:
    5/35
    Comments:
    2
    Kudos:
    28
    Bookmarks:
    5
    Hits:
    564
  4. Tags
    Summary

    Frisk has reached the end of the road in their resets and the strain of their timeline finally gives way right before they can fight with Sans.

    In a last minute feeling of regret, they try something unbelievable.

    They relinquish their soul, and the next thing Sans knows he's laying in a bed of flowers, feeling like he was ripped apart atom by atom and then put back together again.

    Also he has hair.

    And skin.

    And this new Underground he's ended up in isn't quite as friendly as he remembered. Great.

    Language:
    English
    Words:
    83,847
    Chapters:
    15/?
    Comments:
    374
    Kudos:
    653
    Bookmarks:
    105
    Hits:
    12,865
  5. Tags
    Summary

    You had A Plan for your life and it didn't involve getting trapped in your hometown by a new law that monsters and their soulmates must move in together for two years. Papyrus might be adorable, but you don't want anything to do with his antics. Luckily, his brother's soulmate, Frisk, has an escape plan.

    (Based on the Papyrus/self-insert prompts from Scrambledmeggys)

    Language:
    English
    Words:
    27,697
    Chapters:
    17/30
    Comments:
    78
    Kudos:
    80
    Bookmarks:
    11
    Hits:
    1,490
  6. Tags
    Summary

    When your creations turn into reality, things were never meant to go well. Both you and your brother turn into the characters that both of you created and dread to be in. An alternate universe full of death and war.

    -----

    You were tired from this. Hell, both of you were. You were placed in the front lines while your brother created dangerous explosives. All of this just to survive, to live for another day. All memories are forgotten of who you once were before this painful life.

    Who knew a sudden mishap of a machine could be a savior for the both of you?

    Language:
    English
    Words:
    13,786
    Chapters:
    7/?
    Comments:
    110
    Kudos:
    477
    Bookmarks:
    142
    Hits:
    5,852
  7. Tags
    Summary

    Where you, as the reader, are Sans. And your best friend is.. Papyrus? And now theres Sans? And Papyrus? And Papyrus and Sans and.. This guy says his name is Dust? And that guy looks like he's covered in gunk, and why is this Papyrus calling himself Stretch?

    Blurb;

    “Do we call each other Sans and Papyrus?” He beats you to the question the moment you open your mouth, startling a chuckle out of you. You walk over to him, draping yourself over his shoulders with a long-suffering sigh. “I guess I could just call you bro. Are you the older of us now?” You blink, looking at him through the mirror.

    No update schedule, I can barely remember to write. Ill try though!

    Language:
    English
    Words:
    35,474
    Chapters:
    9/?
    Comments:
    40
    Kudos:
    191
    Bookmarks:
    46
    Hits:
    2,221
  8. Tags
    Summary

    The Puzzle Honey Bandits are at it again!

    Their reign of terror must end!

    We all know they are monsters who only burgle other monsters.

    What fiends they must be?

    Who would dare?

    They need to be brought down, by any means!

    Language:
    English
    Words:
    14,206
    Chapters:
    6/?
    Comments:
    33
    Kudos:
    11
    Bookmarks:
    3
    Hits:
    202
  9. Tags
    Summary

    Even though monsters were already part of human society, you didn't really know how to react when you found your dog attacking a random monster in the street.
    Mortified, you got yourself promising him you would do him a favour in exchange of ignoring what just happened.
    Things get worse when you realize he also works at the same building as you.

     

    Do you like angst? This is your fic. Don't worry, you'll laugh too.

    Language:
    English
    Words:
    131,115
    Chapters:
    44/?
    Comments:
    443
    Kudos:
    735
    Bookmarks:
    106
    Hits:
    18,204
  10. Tags
    Summary

    Papyrus is kidnapped by two humans (Underfell Sans and Papyrus) and they have a lot of work to do with the lucrative skeleton.

    Language:
    English
    Words:
    15,594
    Chapters:
    9/?
    Comments:
    9
    Kudos:
    30
    Bookmarks:
    3
    Hits:
    1,031
  11. Tags
    Summary

    It was the only job you could grab. Along with the apartment-life blues, and your college education still ahead of you, could your setting be any more typical?
    Maybe...if some of your regulars hadn't emerged from several feet underground a few years ago.
    But, darn it, you chose this particular store for a reason, and you were going to show these fascinating new faces in and out your door with a smile that (surprisingly) has nothing to do with the fact that you were getting paid for it.
    Good thing, too, because you might get to make some bone-ified new friends in the process.

    Inspired by several AO3 users (listed in the first chapter notes)

    Language:
    English
    Words:
    257,880
    Chapters:
    31/?
    Comments:
    699
    Kudos:
    2,623
    Bookmarks:
    535
    Hits:
    68,576
  12. Tags
    Summary

    With the magical healing powers of ketchup, Sans survives a genocide run--but the rest of his world doesn't. He sets out across the multiverse searching for a family he refuses to believe is dead, struggling to master his new ketchup powers and making enemies every step of the way. When a rival emerges, he's forced to choose between his past and future or risk losing both.

     

    (Yes, this is absolute crack. Yes, this is stupid. But I found out there was no AU where Sans's soul is literally ketchup and for some reason decided that was a problem I had to solve. There will be family fluff, plenty of angst, a bunch of AUs, and general shenanigans and hijinks. I'm treating this seriously enough that I forgot how ridiculous this was until I had to write this summary.)

    Language:
    English
    Words:
    15,607
    Chapters:
    10/?
    Comments:
    32
    Kudos:
    41
    Bookmarks:
    7
    Hits:
    405
  13. Tags
    Summary

    This is my first story on here first and foremost, so please be nice. This is my own work, please do not copy it. I will try to update at least once a week. The first chapter is kind of short but I plan on making longer chapters going forward.

    He's the judge, but what happens when he finds out he's not the executioner? Follow Echo as she finds out who she is supposed to be. War will be waged and maybe the prophesied angel will descend to save the denizens of the Underground.
    But who's trying to stop them and how do they know her?

    Language:
    English
    Words:
    6,441
    Chapters:
    3/?
    Kudos:
    2
    Hits:
    16
  14. Tags
    Summary

    Twelve chapters of the Sans AU's, starring the Star Sanses! (Told in 3rd person omniscient but mainly focusing on Ink's perspective)

    Thanks for reading and I love you all.

    Language:
    English
    Words:
    4,694
    Chapters:
    5/12
    Comments:
    10
    Kudos:
    6
    Bookmarks:
    1
    Hits:
    130
  15. Tags
    Summary

    You’re six months into your career as an electrician and for the first time in your life, you’ve got your shit together. Go you!

    When the job brings you to a mansion inhabited by skeleton monsters and your ex-girlfriend, things change. The wiring in the house is fried, the skeletons are suspiciously evasive about the basement, and your ex keeps inviting you for sleepovers.

    You just want to get through the repairs without setting the place on fire. Keeping your sanity intact would be a nice bonus.

     

    Or, another anti-harem fic, but in this one, the girlfriend is into you too.

    Series
    Language:
    English
    Words:
    74,170
    Chapters:
    12/?
    Comments:
    615
    Kudos:
    881
    Bookmarks:
    234
    Hits:
    16,545
  16. Tags
    Summary

    The color symbolized alot of things once the monsters came to live with humanity. Blue was your favorite color. It stood for stop. It's also a reminder of your ex. Now a skeleton comes at an unstable point of your life. Why does he look so much like your ex Sans? Why does he have stars for eyes?
    And thats the beginning of a crazy spiral of skeletons that don't want to leave you alone. Did I forget this guy calls himself Blue? Love and misunderstandings begin! #this will crash and burn #Enjoy the dumpsterfire

    guess what?! Your gonna get a harem girl!

    Language:
    English
    Words:
    269,769
    Chapters:
    51/?
    Comments:
    305
    Kudos:
    562
    Bookmarks:
    121
    Hits:
    16,531
  17. Tags
    Summary

    Have fun and request away!

    Series
    Language:
    English
    Words:
    7,524
    Chapters:
    31/?
    Comments:
    64
    Kudos:
    10
    Bookmarks:
    2
    Hits:
    973
  18. Tags
    Summary

    After being cheated on by your now Ex Boyfriend (with your best friend no less), you decided to go back to your roots and visit your grandmother. Much to your surprise, she has adopted a gaggle of skeletons who make her big house livelier. Go figure. You might stick around longer, just to make sure these skeletons aren't bad to the bone.

    Language:
    English
    Words:
    114,043
    Chapters:
    23/?
    Comments:
    868
    Kudos:
    1,063
    Bookmarks:
    260
    Hits:
    22,668
  19. Tags
    Summary

    You find yourself sleeping in your car in winter. Being strong enough to get out of an abusive cheating relationship, you opt to sleep in your car rather than be stuck in a bad relationship. While you are wracking your brain to find a solution to your situation, you run into an old school friend and her pack of skeletal boyfriends. Your own situation not being the best, you want to avoid stepping into the situation, however one skelly just can’t let you freeze in the cold. What comes next is a story of betrayal, healing, and helping those that haven’t yet learned to help themselves.

    Mutt didn’t like the human that the rest of his house has as a datemate, what he didn’t count on was ending up falling for the one person that might be able to help everyone in the skeleton household.

    Language:
    English
    Words:
    500,178
    Chapters:
    187/?
    Collections:
    1
    Comments:
    2,131
    Kudos:
    1,650
    Bookmarks:
    301
    Hits:
    75,505
  20. Tags
    Summary

    ~Ava’s Guide to Invading the Multiverse~
    Step One - Go Fishing

    Language:
    English
    Words:
    365,419
    Chapters:
    126/?
    Collections:
    5
    Comments:
    3,283
    Kudos:
    1,925
    Bookmarks:
    231
    Hits:
    47,953

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