Sanster
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Alphys gets depressed and does some things she regrets, which ends up sucking for everyone.
Tis an AU, my friend.
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In which a chronically late and immature scientist thinks it'd be hilarious to 'prank' his boss by using his sex toys without permission.
Results: Gaster breaks his favorite coffee mug and Sans is going to pay for it. -
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Sans accidentally ingests the wrong experimental drug and things get a bit heated. Doctor Gaster is trying his best to remain in control, but he's not about to let his assistant suffer. However, Sans might be the least of Gaster's worries.
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A collection of interactions between a scientist with a crush and a clueless captain. Set in the AU by Demorrtis where Gaster is a Royal Guardsman instead of the Royal Scientist.
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....Behold, the thirteenth wonder of the natural world, a true freak of nature, a blunder of god! But possessing such talents! Hear them tell puns and create puzzles! Come one, come all...
The voice called to the monsters and humans, fueled by intrigue.Never had Doctor Gaster thought he would find a creature as lovely as them...
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Sans just got an internship working for Dr. W. D. Gaster.
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A Letter You Never Wrote For a Friend I Never Was by orphan_account
Fandoms: Undertale (Video Game)
12 Aug 2016
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“Dear Sans, I’m sorry”
It’s a Font you’ve never seen before.
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Gaster is a magical vampire and needs to feed on the magic of others to sustain himself. Luckily for him, Sans is someone who is perfectly willing to be fed on... Maybe a bit too willing.
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Lots of sin here, mostly of the skeletal variety. Every chapter title will tell you what pairing and the really bad stuff, with detailed warnings in the summary for the chapter.
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100 word or less drabbles that I occasionally do on Tumblr.
Series
- Part 29 of Drowning in Drabbles
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Gaster decides to test the importance of intent in monster sexuality.
Finished with the series? There are spinoffs and an alternate ending here.
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It's Okay Because I Love You by Dirtybrothershipper
Fandoms: Undertale (Video Game), Undertail - Fandom, Undershag - Fandom
15 Mar 2017
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This is the story of Papyrus and Sans growing up with Gaster in my AU, Illusiontale, where all of the monsters are much more dangerous- especially because a lot of them tend to act upon their animalistic instincts.
This story WILL INCLUDE: fontcest, sanster, smut, threats of death, suicidal tendencies, some fluff, gore. Please beware. -
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Gaster has an experiment in mind for his new Subject Sans, and Sans is in for a bad time.
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This was only a nightmare, he would wake up soon, he was sure of it.
...But then the nightmare touched him.
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Something was bound to go wrong
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A series of Gaster-centric one shots.
Latest chapter:
Maybe your time together had shown you his human side, the quirky, fun loving personality behind the cold, killer exterior.
Stockholm syndrome might also have something to do with it. A lot to do with it.
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For rag--tag on tumblr's Sanster Week 2017. The chapters form a loosely connected narrative set after Breeding Machine. If you don't want to read that, just know that Sans is carrying Gaster's child.
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- Part 2 of Sanster Continuum
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Sans and Gaster have some fun on the work floor. (Repost from my old account)
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Kink based one shots for
the month of Octoberwhenever. Please make sure to read the info at the beginning of each chapter for tags and warnings. -
Thunder - Sans x Gaster One-Shot by Blue_Boy_2000, CrimsonFandomTrash (Blue_Boy_2000) for Doodle_Famous
Fandoms: Undertale (Video Game)
05 Nov 2017
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In which Sans is scared of thunder and needs some reassurance that it can't hurt him.
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Bookmarks which have used it as a tag:
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Sans tries to get Gaster to get some rest. It's definitely not a date.
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love in the underground is a lie.
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Gaster and Sans get indecent on the work floor
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Gaster returns home late to find the boys .. occupied. That just won't do.
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In which a chronically late and immature scientist thinks it'd be hilarious to 'prank' his boss by using his sex toys without permission.
Results: Gaster breaks his favorite coffee mug and Sans is going to pay for it.- Language:
- English
- Words:
- 10,667
- Chapters:
- 4/4
- Comments:
- 152
- Kudos:
- 1,301
- Bookmarks:
- 124
- Hits:
- 21,958
Bookmarked by Puffi32
17 Sep 2016
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Bookmarker's Notes
Most amazing shipping finished fanfiction I've ever read.
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love in the underground is a lie.
Bookmarked by Jeyawue
30 Sep 2016
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Bookmarker's Notes
gaster->sans threat
Papyrus->Sans
Protect him -
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Sans becomes Doctor W.D. Gaster's lab apprentice, his ultimate dream job, but despite everything things are not always what they seem, and eventually it becomes apparent that Doctor Gaster has other plans in store for him.
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Sans tries to get Gaster to get some rest. It's definitely not a date.
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To say Gaster is an unusual Monster is a woeful understatement.
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Saloon! Au Swapfell It’s based in the wild west. Papyrus is desperate for a job and when a wealthy doctor and his son require the use of a farmhand. But when the doctor has to travel into the city, his angelic, soft spoken boy turns into a sexual deviant who’s eager to drag Papyrus down with him.
But Papyrus won’t be swayed...or will he? -
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Ah... Valentine's Day. Love is in the air. So why not have some ships, shall we? And who isn't shipped more than Sans?
Sans and Toriel go on a date at Grillby's. If you took a look at the tags, you'll know it doesn't go well.
Bookmarked by thekingoftrash
30 Jan 2019
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Bookmarker's Notes
this is the greatest thing i've ever read
it has literally every ship in it
sans is a heartbreaker... in more than one way winkwink ;) -
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Gaster has a new machine, and Sans is the test subject.
Set in Underfell. More horrifying kinks than you can shake a stick at, featuring involuntary breeding experiments and guest starring eggs.
Please read the tags and take care of yourself; don't read things that gonna be a bad plan, man. If you're way into bad plans, then come on in.
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Gaster and Sans for nearly two years have been seeing each other. They've been enjoying the experience thus far as well. But like every couple they have their problems, and unlike other couples they have one specific, BIG problem. The fact that they are father and son, and have to keep their taboo relationship a secret from the entire underground.
But is it a secret worth keeping? It may prove to be more trouble than it's worth for the two skeleton monsters.
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Papyrus stumbles across some things he never knew about his brother or himself.
Honestly the summary makes it sound better than it is but in all honestly this is a cringe fest of terrible writing. I'm actually considering rewriting( of course I'd still keep the premise of the story but I would make it less terriable)
[Currently on hiatus]
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[Drabble] Before the accident in the CORE, before the creation of Papyrus, Gaster had a secret project he was working on -- a manufactured monster, Sans, born of his own bones. When one locks themselves in a laboratory basement for weeks on end, though, one grows callous in the pursuit of satiating certain urges.
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goddamn, we missed the vein by cashtastrophe
Fandom: Swapfell - Fandom, Underfell - Fandom, Undertale (Video Game)
28 Jun 2025
- Words:
- 164,577
- Works:
- 10
- Bookmarks:
- 48
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everyone learns faster on fire by cashtastrophe
Fandoms: Undertale (Video Game), Underfell - Fandom
15 Jan 2021
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When Papyrus is nearly fifteen, sans gets sick.
sans gets *really* sick.
(sad fell pap noodling because reasons? this is primarily a standalone but it does tie in to the rest of the series if u really wanna wreck ur whole day)
Series
- Part 4 of goddamn, we missed the vein
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Serious note: This is dubcon in places, though consent is acquired later- it's questionable at best, and manipulative. Please mind the tags.
Happy holidays! This is a Fontfest fic that kinda spiralled out of control XD
Au-ish, still the classic UT setting but Sans and Papyrus live with Gaster at the Hotland labs instead of Snowdin... That and Gaster isn't in the void obviously :')
Hope you enjoy! -
Day 11: Sadism/Masochism & Gags by Ked_from_safe-skeletons (Sinnychild)
Fandoms: Undertale (Video Game)
26 Oct 2017
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Sans always disobeys. Gaster will make this stop.
Series
- Part 2 of Kinktober 2017
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- Words:
- 127,191
- Works:
- 8
- Bookmarks:
- 21