1 - 20 of 4,296 Works in Alternate Universe - Underfell (Undertale)
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Summary
A stand-up comedian with a bad temper and low motivation ends up falling for Frisk's homeroom teacher, her irritatingly soft voice, and her smug attitude.
Who would've known?
There's probably a lame old joke hidden in there somewhere, but he doesn't give a damn about that right now, so maybe come back later, and he'll think of something.
(Mostly told from his perspective, but there will be chapters featuring Second Person POV.)
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Would You Be Mine If I Asked? by FandomWorld9728
Fandoms: Undertale (Video Game), Underfell - Fandom
02 Aug 2025
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Sans couldn't believe he just did that! Stupid, stupid, stupid! When the Dean was going to refuse to give him the job because he didn't have a human partner, he lied straight to the man's face and said he did! Now he was expected to bring them to a facility party to prove that they exist.
Where was Sans supposed to find a human to 'date' him in a week? It's not like a human willing to spend any amount of time with him was just gonna fall out of the sky. And if they did, they most likely would laugh in his face about pretending to be his partner.
"Hey, Sans. Did you get the job?"
Series
- Part 5 of Sans/Reader Fics
- Part 6 of Undertales Across the Multiverse
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What if you're finally free? On the surface with all your dear friends? But then an incident...
What if a reset happens?
I'm back with another what if for my first fic (a new life with a bunch of monsters (and annoying humans))
God i need to stop😭Series
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Reader is a lawyer who was looking for a cheap room for rent. After Papyrus left to study abroad for culinary arts, Sans was down to let her stay in his brother’s room for a fair price. They both have a great roommate relationship; they don’t know each other that well yet, but Sans makes her laugh.
One day, she walks inside the apartment, wondering if she was seeing double or if there were two identical skeletons in the middle of the living room.
Yeah, a second roommate was never mentioned on the lease.Series
- Part 1 of Three idiots
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Papyrus and Sans fight. Sans disappears. He returns much later with a strange alternate version of himself.
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She has a feeling that today is going to be a bad day.
She has no idea how bad it's going to be until Red gets home and there's a look in his eyelights she hasn't seen before.
Turns out she's not his soulmate.
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Waking up buried in snow, alone, and with no memories but basic common sense?
Check.
Seeing numbers, words, and broken code floating around every object and surface?
Also check.
Looking like a walking system crash—with one eye red, the other computer-blue, and a body flickering like corrupted a light?
Triple check.He doesn’t know who he is.
He doesn’t know what happened.
And most importantly...
He doesn’t know why everything feels like he shouldn't be alive.Everywhere he looks, the world speaks in code—and he can read it like instinct. Names, stats, system files, broken timelines. And yet, the more he tries to remember, the more he feels like a mistake.
Note from the Me:
This is my take on Fatal Error—a much more none canon, wandering version of him. He’s not fully canon-compliant inn terms of power and has a different origin and personality. It’s a reimagining: glitchy, lonely, and filled with questions, bad puns, power and some more bad puns. -
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Summary
You are a one-of-a-kind human being, and you can't let anyone capture you.
Everything was fine until you encountered these skeletons while sailing the seas undisturbed.
And they seem to be a little too interested in you now. They won't let you go that easily.
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A (possible) collection of spicyhoney sickfic and adjacent one shots
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*I don't use Y/N*
Monsters have settled in after being freed from their underground prison. This story is how you fell through into different universes and timelines, along the way to stop yourself from falling randomly into these different timelines, you find that SOULmates can cross the barrier of universes and timelines.
Writers Note: Unfortunately this will never be finished as I've rewritten it, find the new version at this link: https://archiveofourown.info/works/68454546/chapters/177187116
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You and your fuck buddy's relationship
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TV Time Studios, a king of the entertainment industry. Run by the big man himself, Mr. Ant Tenna. A man willing to do just about anything to stay relevant. After social media makes Cyber City take off as a go to technological destination, it's decided that they should probably hop on that train as well.
That's where you come in. An accomplished social media manager, several saved businesses under your belt, a winning smile, and something that attracts your new bosses attention.
IT'S! T! V! TIME!
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a new life with a bunch of monsters(and annoying humans) by Naryhey
Fandoms: Undertale (Video Game)
30 Jul 2025
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y/n y/l/n is one of the people that has access to the magic in their SOUL. so she's working where everyone with magic that wants a legal job works, plus it pays real good. but when she falls into the underground she has to look for another house, another job and of course start a new life all over again. but turns out the poeple of the underground aren't that friendly.
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An Unexpected understanding by Ari_Artzzz404
Fandoms: Undertale (Video Game), Underfell (AU)
30 Jul 2025
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when the monsters finally were freed from the underground, the humans were outraged, though that was to be expected, humans tend to be afraid and disgusted by things the don't understand, and they didn't know the whole story, And the monsters were wary and cold towards humans due to this.
therefore, the tension between humans and monster remained at a constant high.
Y/N was a human who wanted to understand. At first they were wary of monsters, they didn't hate them, they knew that at a lot of the things humans say about them are probably wrong, but they never really knew or not, so they were overly anxious around them, especially with a SOUL defect already making them anxious. until an event with a monster makes it clear to them that human bias is true sin, and that it was time to be open their mind and change.
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Sans wakes up with a splitting headache and no idea why there's a new crack on their skull. As it turns out, that was actually the least of his worries, because when he meets a more deadly version of himself, he suddenly realizes he may not be in Kansas anymore...
Series
- Part 1 of Graceful Mistakes
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It takes 10 Skeletons, not a village by Donewith_life
Fandoms: Undertale (Video Game), Underfell (alternate universe), Underswap (Alternate Universe), Swapfell purple (Alternate Universe), Horrortale (Alternate Universe)
29 Jul 2025
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You mum drags you to her boring science lab, forcing you to help her with her research, against your will and interest, until late at night. You're in a lab late at night, what could go wrong?
(Reader is 15 so NOT a romance between reader and the skelebois.)
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Head Over Heels (process of being rewritten) by Sl1mShadyNeptume
Fandoms: Undertale (Video Game)
29 Jul 2025
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For as long as you could remember, you’ve been scared of your secondary gender. Especially when you started getting older and started to realize how against you the world was.
How you expected only to be an Alpha’s omega…and that’s all you were supposed to be…not even your own person…you didn’t like that!!
Because of this, you’ve made a promise to try and avoid relationships, live life for yourself and just try to stay safe without help from an Alpha.
It was going good until you were slammed up against shelf in the grocery store by a Skeleton that would claim to be your Alpha. Since then, Your life has spiraled down and you are doing everything you can to keep calm while a giant skeleton follows you around like a puppy.
Good luck dealing with Monsters who hate you, Alpha’s who want you for then wrong reasons, A human who saved a race of people wanting you too be their older sibling, A annoying roommate , your ‘Alpha's’ brothers trying to kill you for being human and Said Alpha being the worst himbo!
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Their King is dead. The six Souls are Gone. Their future lays in ruin.
Frisk has slipped through the barrier and left the monsters with shattered hopes and a toppled monarchy. With no witnesses, it was pure, selfish regicide. They were loved by all, and thus, their betrayal cut all the deeper. For the third and final time, humans had stolen everything from them.
Anger has a way of changing people. It remains in the Soul even as memories fade.
Frisk may be gone, but the RESETS continue, multiplying the resentment within them and morphing the residents of the Underground into tightly wound reflections of their former selves. No longer in a position to do nothing, Sans is Determined to find a way past the barrier for the sake of his brother, and for the sake of vengeance.
He’ll give anything to achieve that goal. His Soul included.
He’d found an alternate method that should work, buried deep inside a gilded dusty tome in the royal library. Instead of using LoVe to pass through the barrier, Sans was going to use love. He was going to have to gain a consenting human, and convince her to bind her Soul to his. Permanently.
Series
- Part 4 of The Butterfly Effect 💚💛🧡💜💙🩵❤️
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Hunger Pains, Famine Gains (Adopted by Elliot) by TheBloodiestEclipse
Fandoms: Undertale (Video Game)
28 Jul 2025
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Hungry. Hungry. Hungry. Hungry.
I am Hungry
I have been hungry
I was born hungry
What do I need?
Hungry. Hungry. Hungry. Hungry
Series
- Part 1 of Gore, Violence, and Pure Pain | Stories
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Kiss Me, Kill Me (And a Secret Third Option) by Embrace_the_Deep (DefinitelyNotABee)
Fandoms: Undertale (Video Game)
28 Jul 2025
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What had Ink tried calling him again?
Someone named Killer?
As fitting as that name would have been for the previous owner of his body, he clearly remembered that he had been referred to as 'Sans' in the blurred bits of memories.
Maybe he was being mistaken for someone else.
He hopes he never meets this actual 'Killer', but even if they were some sort of shady person- skeleton- thing, that doesn't excuse kidnapping a stranger and chaining them to the floor of your home after nearly killing them!
With the most unimpressed expression he could muster, Quill forced the aching phalanges of his right hand into a wrist-up fist, and extended his middle finger.i.e. A self-indulgent crack-treated-seriously fic featuring isekai!Killer vs. the Multiverse. Enjoy!
Series
- Part 1 of The Third Secret Option