Sans (known as Blueberry or Blueberry Sans by some fans) is a main character in Underswap. He has his personality swapped with Papyrus, his brother.



Sans is a skeleton of short stature who usually wears his "battle suit", that is composed of a gray piece with padded sleeves, a blue bandana around his neck and blue gloves and dark blue shorts, in addition to wearing light blue boots too.


Sans is very sure of himself and is somewhat immature, but very clever due to his love of puzzles and riddles. He has a big heart and always thinks the best of everyone; this is why his brother is always in constant care of him. He also love to make tacos (but they don't taste good).


Sans tries to act cool in the pacifist and neutral routes like how Papyrus mentions. He is also not very good at making tacos, as Papyrus mentioned that he has to make them more edible.

Main Story

Neutral Route

Like Undertale Papyrus, Underswap Sans will first appear when Papyrus hides the protagonist behind an object which prevents Sans from noticing them for the first time. Sans berates Papyrus for being extremely lazy and smoking in that moment. But there is a theory that Sans can see the protaganist, but he thinks that the protaganist is a that object that the protaganist hides from the camera (maybe Sans).

Sans will then notice the protagonist, and will proceed to 'capture' them using his puzzles mainly made by him and Papyrus. At the end of (possibly) Sunnedout Town, Sans will fight the protagonist. However, after 3 times of losing the fight, Sans gives up fighting them and become friends with them instead. The protagonist can later hangout/date with him, which will then give the protagonist the ability to call him in whatever situation and whenever they are.

True Pacifist Route

Like in the neutral route, Sans doesn't act differently in the beginning. In the Pacifist ending, Sans was called to be with the others after Asgore interrupts Toriel from fighting the protagonist. Undyne then asks how Sans managed to invite everyone, and he says that a little "kitty" told him. Right after that, Temmie traps all of them and proceeds to turn into Monster K. Dreemurr

Genocide Route

As usual, Sans will still berate Papyrus and give puzzles to the protagonist. Sans will, however, find them 'different' and notice how they hate puzzles. Sans gives up fighting and still has hope towards the protagonist before he dies. If the protagonist spares him, he will admit that he was afraid. After this happens, everything will go back to a Neutral route.


The Protagonist

Sans is friends with the protagonist in both the neutral route and the pacifist route. Sans likes the way they like tacos, puzzles and being a cool dude.

In the genocide route, Sans wanted to be friends with the protagonist like how he did in the other routes. If killed, Sans has hope for the protagonist before his last minute strikes. If spared, Sans reveals how afraid he was because of the protagonist.

The protagonist remains friends with him throughout the game and gains the ability to call him on the cell phone almost anywhere.


Papyrus is Sans' older brother. He is always there to annoy Sans with this ridiculous puns and lazy attitude. Sans looks after his lazy bones of a brother, but Papyrus always returns him the favour. If Sans dies in Genocide route, the protagonist encounters a battle with Papyrus.


Sans is constantly trying to be part of the Royal Guard so that he can impress Alphys, who is his trainer, and always tells him to go out to find humans and when found, bring them back to her. Overall, they have a pretty strong friendship.


Just like in the actual Undertale, Sans is mentioned, by Papyrus, to have been given advice, flattery, and predictions by Temmie. Completing the flawed pacifist route several times will result in Temmie saying, "So, you're here again. What's wrong with you? Are you trying to start the Temmie Fan Club? Because if you want to join THAT... You'll have to talk to Sans. Yeah, he started one. A few different times, anyway. I won't lie. He's one of the better characters to mess around with. Took me a long time to get bored with that one. ... Yeah. Talk to him about it."



  • Much like Papyrus in Undertale, Underswap Sans also likes a specific food too, this being tacos.
  • Just like Papyrus in Undertale, Underswap Sans will also try to capture the human
  • Underswap Sans is sometimes known as "Blueberry" or "Blueberry Sans".
  • Underswap Sans tries to act cool
  • Sans constantly tries to be part of the Royal Guard to impress his trainer, Alphys
  • Underswap Sans started a Temmie Fan club
  • Sans' brother, Papyrus, is very protective of him.
  • Even though he's never seen it before, Sans disdains anime
  • There is no official Sans sprite yet for Underswap.

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