He has a dream of seeing a human. A couple of his disadvantages are that he cannot teleport, and that he is much weaker than Undertale Sans, but one of his advantages is that he can move as quickly as Undertale Papyrus. He is very cheerful, and much more energetic than Undertale Sans. He is also very positive, and enjoys making tacos for his friends.
For Mweh Heh Heh! and Bonequarrel, click on this link: https://www.youtube.com/watch?v=ssIcciLMwyw
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Like Undertale Papyrus, he has a special laugh, but instead of "Nyeh Heh Heh!", it's "Mweh Heh Heh!" Many fans also see him as the "adorable" variant of Sans.
He is often referred to as "Blueberry" by fans because most of them find him cute, along with the fact that most of his clothing is blue.
He seems to have an extreme intolerance to sugar, as it will make him overly hyper. He also seems to spontaneously combust when he consumes caffeine.
Blueberry is not the official Underswap Sans. He is a fan made version of him.
His arms are by his sides, and he appears standing up straight and still, facing the player like Undertale Sans. He is smiling, but his dimples are missing. (Though the edges of his mouth are tilted up to suggest something like dimples). He wears a blue bandana that appears to have a small hole close to the center. Whether this is an accident or not is up for debate. He also wears gloves like Undertale Papyrus in his battle scene, but they seem to be missing in his overworld figure. He wears a gray sleeveless shirt with a white t-shirt underneath, along with gray shoulder pads with baby blue outlining. He wears pants with a slightly faded blue look to them, and he wears blue shoes that match the color of his bandana.
In Battle AppearanceEdit
He stands in the same position as Undertale Papyrus, but is much shorter. Aside from his dimpled smile, (which is similar to, or if not exactly like Undertale Sans'), his facial expression is mostly like Undertale Papyrus'. His battle sprite reveals that the bandana he is wearing ties up behind his left shoulder, which is something that is not seen on his overworld figure.
When Sans first met Chara, he immediately wanted to be friends with them. He is very happy to have Chara as a friend, but disappointed because he cannot join the Royal Guard for befriending Chara; a human.
Sans is the brother of Papyrus. They are very close even though Papyrus likes to joke around which oftentimes annoys Sans a lot. However, to Papyrus, Sans is the most important thing in the world. Papyrus is generally seen as Sans' protector, but heavily affected by his knowledge of the timelines, expecting to see Sans again even if they were to both die.
Sans and Alphys are best friends. Sans wants to join the Royal Guard, but Alphys secretly will not let him since she cares about Sans and refuses to see him get hurt because he is too nice to properly fight in a battle. They hang out all the time. Alphys is also the one who is training him.
Sans starts a Temmie fan club, as told by Temmie themself in the Neutral Route. It is known that Temmie does not like Sans, but it is unknown what Sans thinks of Temmie.
Sans does not know much about Frisk, but can suspect them in Chara if they were playing through a Genocide Route.