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* But nobody came.

* This article contains information that is from a cancelled AU, an AU that has been put on an "Indefinite Hiatus", or an AU that has not had a story update in a year. As such, some information here may not be found in any established story, and could be considered non-canon.

Time of Last Story Update:

Time of Cancellation:

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* (Seeing an article of an AU you can freely make content for...)

* (It fills you with determination.)

This article is about an AU that has been deemed community-shared, either by the author declaring it, or from long-term abandonment by the author. For elaborated information on community AUs, see the Templates policy page.

Underswap is an AU where many of the characters' roles are swapped, as well as their personalities, though some quirks tend to stick in places, or are modified. Sans is the excitable, confident, extremely optimistic human hunter, while Papyrus is the laid back, protective bro following Chara (who is swapped with Frisk).

Underswap was made by P0pc0rnPr1nce.

Unfortunately, the original creator of the AU has left the fandom, deleted the information on the AU and has no interest in continuing the project, which is mostly caused by Sans being depicted as "Blueberry" and Fontcest.

About the AU

The plot of UnderSwap revolves around each character from the UnderTale universe being swapped with other characters, such as Sans' and Papyrus’ personalities, although they keep the same names, so what we consider Sans to be as a character is now how Papyrus is, for example. They also keep part of their personalities, like how Sans still tells puns.


Canon Changes

Non-Canon Changes



The protagonist of the AU, and the 8th fallen human. They look the same as normal Chara but with a straight face.


A stuffed animal with Monster Kid's dust on it, which came to life when Undyne experimented on it. It has a "Kill or be killed" mentality.


As former king of the underground, he turned his back on his wife to flee to the ruins where he welcomes fallen humans with open arms, caring and trustworthy. He offers you a nice cup of tea instead of a pie.


A small shy ghost in the outskirts of waterfall, dreams about being a TV star someday. Writes romance stories, and would love to share their collection of them with you. He's not pink, a misunderstanding created by the original image's pinkish color. His name is also not Hapstablook, like many people seem to think. He has a heart shaped eye.


Excitable and loving, training to become a royal guard with Alphys. However, as Sans and Papyrus keep their original stats, his low stats prevent him from being accepted. He enjoys making tacos for his friends. His signature laugh is "MWEH HEH HEH", he says "WOWZERS", and calls himself supreme and magnificent.


A laid back jokester who is into practical jokes, though shares a wide variety of other ones with Asgore. Enjoys honey as his favorite condiment and sells corn dogs as a side job. KR still is Sans' thing, and instead he has smarter and stronger attacks, though he is the one who is aware of resets and bleeds after his genocide battle. He wears hoodies with indirect posts on them. He apparently smokes cigarettes (NOT weed), even though he has no lips.


Has a maid cafe in Snowdin town, confident and maybe a little smug. She sells croissants, tea and donuts, uses roller-skates to serve them to people.


Nice and friendly, sells burgers at his portable burger stand. The wrappers have a handwritten compliment on them.


Captain of the royal guard, fierce and unforgiving. Still enjoys her anime and helps Sans with his cooking every now and then. Instead of spear bullets she uses rotating axes. During the genocide route, she turns into "Alpha Alphys". She thinks anime is real.

Ruins Dummy

Ruins Dummy fights Chara out of boredom instead of anger.


Wacky Flowers living in a hidden village.


Royal scientist, reserved and goofy, made Napstaton’s body for him. Enjoys watching anime/cartoons with Alphys. She thinks Mew Mew Kissy Cutie 2 is better than the original, though mostly watches manime and giant robot anime. Just like Alphys in Undertale, she knows that anime is not real.


The most famous radio DJ of the underground, charismatic and masculine (and frankly kind of a douche). Calls people “bro" and "broski” instead of darling. He likes his arms just like Mettaton likes his legs, and has retractable turntables. He uses rhythm based attacks. His name is not Napstabot, like many people seem to think.


Protector of flames in all the underground. He sells fire based food to raise money for the flames in the Ruins. He's wacky and demanding.

Nice Cream Guy

Cynical and shabby, wanted to be a DJ but came to work in the fast food corner of the NTT hotel. He hates his boss.


Queen of the underground, ruthless and persistent. She can’t forgive herself for the lives she took from innocent children. She's more ruthless and emotionless than Undertale Asgore, and uses a scepter as weapon. She offers pie instead of tea.

Monster Kid

Asgore and Toriel's adopted son, who died when trying to free monster kind with Frisk.


Frisk was the first fallen human, who poisoned themselves and died to free the monsters.

Fandom mistakes

A list of things the fandom got completely wrong that should be avoided at all costs when doing anything related to Underswap:

  • Sans is not a small child, he's still an adult.
    • Sans does not wear a bow either, nor is his cape light blue.
  • The name Blueberry or Carrot is not mentioned anywhere.
  • Sans does not hate puns.
  • Sans is not a yandere.
  • Sans and Papyrus don't have glowing tongues or fangs.
  • Papyrus doesn't hate Frisk.
  • Papyrus does not smoke weed.

A few things that are more forgivable but should be watched out for when trying to follow canon:

  • Napstablook's and Mettaton's canon names are Napstaton and Mettablook, not Napstabot and Hapstablook/Mettacrit.
  • Napstaton's screen doesn't use blue.
  • Mettablook is not pink.
  • Hapstabot is not canon.
  • Passive Megalovania is not a canon thing.
  • Papyrus doesn't use orange attacks.
  • Papyrus' condiment of choice isn't mayo.
  • Papyrus doesn't wear a jacket.
  • Sans and Papyrus aren't pink.
  • Sans doesn't have a large hammer as a weapon.
  • Sans isn't addicted to sugary food like coffee, lollipops or muffins.
  • Alphys isn't as slim as Undyne.
  • Alphys doesn't wear an eyepatch.
  • Alphys doesn't have a body pillow of Mew mew.
  • Toriel doesn't have a crown.
  • Toriel doesn't use a trident as her weapon.
  • Toriel isn't in love with Sans, and Asgore isn't in love with Papyrus.
  • Annoying Dog does not wear a blue scarf. He also does not resemble Morty, this was made up in unofficial continuations of the original.
  • Annoying Dog, Endogeny, and the canine unit aren't replaced with cats. This is a role swapping AU, not Oppositetale.


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  • At first, Papyrus was going to drink mayonnaise instead of ketchup, but they thought honey would fit Muffet’s better.
  • The original idea of Underswap was never a full personality swap, though Frisk/Chara, Flowey/Temmie and Burgerpants/Nice Cream Guy do fully swap personalities.
  • It's stated Muffet’s is overpriced instead of Grillby’s selling points. But later on, it's stated Grillby's is the overpriced one.
  • Papyrus and Sans swap their use of upper and lower case, but not their fonts, obviously.
  • Originally, Undyne was supposed to love cartoons instead of anime, though it was later changed.
  • Originally, Bratty & Catty were supposed to just swap their clothes, but it was scrapped due to not making sense.
  • Asgore was originally supposed to bake cakes instead of pie.
  • It is officially stated that Jerry will never be swapped in this AU.
  • In a joke twitter post, Popcornpr1nce claimed that Hatsune Miku had become the new owner of Underswap. This post later was deleted however.
  • Due to the fact that there are multiple versions of Underswap, the original AU is somethings referred to as Canonswap or Classicswap by fans.
  • There are 3 non-canon swaps that are commonly used in Underswap takes, these being Flowey - Echo Flower, Asriel - Chara and Gaster with himself, but with a more optimistic and cheerful demeanor.
    • Until the Underswap research doc's creation and discovery, the Monster Kid - Asriel and Gaster - River Person swaps were seen as non-canon.