Sans

 (/sænz/, SANZ) is the older brother of Papyrus, and a major character in ''Undertale. ''He first appears in the forest before Snowdin town. He is a supporting character in the Neutral and Pacifist Routes, while being the final boss and heroic antagonist in the Genocide Route.

Appearance
is a short and big boned skeleton, with a perpetual grin on his face. He wears an unzipped hoodie, a white t-shirt or sweater, black shorts with white stripes and a pair of sneakers or slippers.

He has white pupils, which tend to disappear when he is serious. When using magic, his left eye flashes cyan and yellow and his right pupil disappears.

Personality
is shown to be very laidback, sleeping on the job and taking breaks often. He enjoys making bad, skeleton-related puns; although the fact that he performs at MTT Resort hints that he may in fact be a talented comedian. He likes science fiction and loves to drink ketchup. In addition, he hates making promises.

He is kind and reassuring but becomes eerily serious at particular moments, sometimes causing his pupils to disappear leaving empty black sockets. He is also very observant; his lines and actions change in relation to the protagonist's choices more than any other character's.

's laziness is shown to be in fact apathy and fatalism. He wonders if his indolence stems from his knowledge of the fact that any progress he makes will be erased abruptly as soon as the timeline resets, though he dismisses it as an excuse for being lazy.

Judging by the quantum physics book, workshop, and broken machine found in his house; among other evidence, is heavily implied to come from a scientific background.

Abilities
is shown to be able to move exceedingly quickly and/or teleport through his frequent use of "shortcuts", as he calls them. In battle, he shoots what appear to be a kind of laser or beam using "Gaster blasters", a device resembling a goat or dragon skull. These also bear similarities to the DT Extraction Machine found in the True Lab, Gyftrot's head, and Asriel's first form's head.

He has obtained the knowledge of multiple timelines and the SAVE function, presumably through his scientific research. However, it appears he does not actually retain knowledge when the protagonist loads a SAVE, and cannot use the SAVE function himself. It may be that his awareness of the situation and his innate perception allows him to recognize when the protagonist is behaving unusually.

seems to know if the protagonist has achieved an impossible ending in the Neutral Route's phone call and will call them a "dirty hacker". Given that this also counts as an error handling message, he is aware of when the game's code suffers bugs as well.

is also shown to have some skill in playing the trombone, though he is only seen playing it once. Papyrus finds his "incidental music" annoying, so he must play it on other occasions.

Neutral Route
first meets the protagonist after they walk out of the Ruins into Snowdin Forest. They are pursued by, who first appears as a silhouette. After introducing himself, he explains that despite being a sentry, he has no interest in capturing humans, although his brother, Papyrus, does. He then hides the protagonist from his brother behind a conveniently shaped lamp, while he and Papyrus have a heated discussion of 's laziness and the importance of puzzles. appears multiple times throughout Snowdin Forest, usually alongside Papyrus, observing and commentating on the puzzles but not actively engaging in any japery, except for the word search.

is absent in Snowdin Town, although he appears abruptly during the protagonist's date/hangout with Papyrus, sticking out of his room with a trombone. If the protagonist kills Papyrus, is absent throughout the rest of the game, until he resurfaces to give his judgement.

After entering Waterfall, is found manning another sentry post, and asks if the protagonist wants to hang out with them. If the protagonist agrees, he takes them to Grillby's via a 'shortcut'. is greeted warmly by the patrons of the diner, and proceeds to treat the protagonist to a burger or some fries. After some ketchup nonsense, a spotlight falls on him and the protagonist. then tells the protagonist that Papyrus has mentioned a flower has been talking to him, and mistakenly believes that someone is tricking him with an Echo Flower, when in reality the flower in question is Flowey.

is met again in Waterfall, and pranks the protagonist with a red-eye telescope.

The protagonist passes him sleeping at one of the sentry posts in Hotland when fleeing from Undyne. Once Undyne notices him sleeping, she becomes quite angry, causing her to stop to berate him.

is also encountered later on in Hotland selling hot dogs. If the protagonist attempts to buy a hot dog with no room in their inventory, he will begin to place the hot dogs on their head. He will stack up to a maximum of 29 hot dogs. cannot stack anymore, saying that he can't reach that high.

is later found outside of MTT Resort, where he offers the protagonist to grab a bite at its restaurant. If they agree, he will escort them through one of his 'shortcuts'. At the restaurant, reveals he had befriended a woman with a similar affinity for puns that resided on the other side of the entrance to the Ruins. He tells the protagonist that the woman made a request to which he promised to comply: to watch over and protect any human who came through the door. He states that if not for his promise, the protagonist would be "dead where [they] stand", which he dismisses as a joke shortly afterwards. He mentions how he's doing a good job at protecting the protagonist, though he will question it if they have died before. Before leaving, he tells the protagonist to take care of themselves, because there's someone who really cares about them.

Judgement
While passing through the final corridor, encounters the protagonist one last time. He proceeds to judge them for the EXP earned throughout the game, revealing that EXP stands for "EXecution Points", and that LOVE stands for "Level Of ViolencE". His judgement is determined by the protagonist's actions throughout the game.
 * If the protagonist gained no EXP, will begin to talk normally and will skip his judgement, telling the protagonist that they never gained any LOVE, but that they gained love, and that they have always striven to do the right thing. He goes on to say how he appreciates the protagonist for having kindness in their heart, telling them that the Monsters' fate is in their hands; they can either let Asgore take the protagonist's soul for their freedom, or take Asgore's soul for the protagonist's escape. He tells the protagonist that he believes their determination will help them do the right thing. He then leaves.
 * If the protagonist restarts from a SAVE Point after hearing his speech, will take note that the protagonist has already heard this speech before and will give them a secret codeword. The protagonist can repeat this about two more times until  gives them the key to his room.
 * If the protagonist gained some EXP, will give them a moment to think on their actions. After a moment, he will begin to talk normally, and will tell the protagonist that all that matters is that they were honest with themself.
 * If the protagonist spared Papyrus but killed other monsters, Sans tells the protagonist that it will be left up to them to decide what will happen. He then leaves.
 * If the protagonist resets after hearing his speech, then returns to the Last Corridor, judges the protagonist based on how high their LV is:
 * If the protagonist is at LV 1 (but has more than 0 EXP), presumes that they killed someone just to see what he'd say about it. He says "wow. you're a pretty gross person, huh?"
 * If the protagonist is at LV 2, says that it's pretty sad that the protagonist messed up the slightest amount, and that they probably didn't know what they were doing, but then says that he's kidding, stating: "who gets to LV 2 on accident? get outta here."
 * If the protagonist is at LV 3, gives the protagonist a C+, and tells the protagonist that they can do better.
 * If the protagonist is above LV 3, says that they probably killed some people on purpose, though maybe some of it was in self defense, and that he's not sure, as he wasn't watching.
 * If the protagonist is above LV 9, says that doesn't mean that the protagonist is 50% good, and questions "what can I say that will change the mind of a being like you...?"
 * If the protagonist is above LV 14, will say that the protagonist is a "pretty bad person, " but that they could be worse, and that they "pretty much suck at being evil."
 * If the protagonist killed Papyrus, goes on to tell the protagonist that he suspects they have some sort of special power, and asks if they think it should be their responsibility to do the right thing.
 * If the protagonist says "Yes," he then asks why they killed his brother.
 * If the protagonist says "No," he says that he won't judge the protagonist for their viewpoint, but calls them a "dirty brother killer."
 * Either way, he will leave after reminding the protagonist of Papyrus's death at their hands.

Endings
After the fight with Photoshop Flowey, will call the protagonist, and inform them of the events that transpired after their departure. The content of this phone call varies depending on the protagonist's actions, and a list of the different endings which Sans can describe is found on the Neutral Route page.

True Pacifist Route
appears during the cutscene that occurs after the protagonist initiates the battle with Asgore. Toriel recognizes his voice, and they meet face-to-face for the first time. Toriel recognizes Papyrus as his brother, saying that Sans has told her a lot about him. , along with the protagonist's other friends, are bound by Flowey, yet still protect the protagonist against Flowey's attacks. However, is absorbed by Flowey, along with all the other monsters and their souls.

During the battle against Asriel, appears as one of the Lost Souls.

After defeating Asriel, stands alongside the other main characters. If the protagonist talks to him, he says a certain remark depending on what, if anything, the protagonist said to Toriel in calls at the beginning of the game. also uses Toriel's phone to text for her a few times, as Toriel's thumbs are too big for the phone buttons. After the protagonist is ready to leave, exits the Underground and heads to the Surface along with the other monsters.

Papyrus runs off to introduce himself to the humans, and says someone's got to keep him away from trouble, and runs off in the opposite direction presumably to use a 'shortcut'.

In the credits, is seen riding a tricycle on a highway, while his brother races alongside him in a car. Papyrus seems irritated when his brother overtakes him.

Genocide Route
stalks and introduces himself to the protagonist as usual, and although he recognizes the protagonist as not being human, he asks them to keep pretending to be human, as Papyrus has always wanted to see one. He goes along with Papyrus's japery, although he does not appear as an NPC as he does on regular routes. After the protagonist crosses the bridge, warns them not to fight his brother, or else they'll "have a bad time." He then suddenly disappears, and is absent until the final corridor.

If the protagonist aborts the Genocide Route by sparing Papyrus, will reappear at the Waterfall sentry station, and tell the protagonist he respects them for doing that. He will continue to appear as if on the Neutral Route, but will not take the protagonist to Grillby's, since there's no one left in Snowdin.

In the final corridor, asks the protagonist whether or not a person can change. Not expecting an answer, he continues and asks if they "wanna have a bad time? ", warning them to not take another step forward. After the protagonist continues forward, then engages a fight against the protagonist, and apologizes to Toriel (who is absent) for breaking his promise to protect the protagonist.

After some short monologue, begins a furious onslaught of attacks against the protagonist, while contemplating why he has not done much to prevent the protagonist's actions. After he finishes his speech, offers to spare the protagonist, telling them that accepting will make his job a lot easier.

If the protagonist spares him, he tells them that he won't let the protagonist's work go to waste. He then kills them with an unavoidable attack, and asks them in the game over screen not to return if they really are a friend. If the protagonist does come back, 's second attempt to convince the protagonist to spare him is a little half-hearted, suggesting that he knows the protagonist has already fallen for it and is unlikely to do so a second time. When the protagonist attacks him, he says that means they never really were friends, and asks the protagonist not to tell other instances of in other timelines.

If the protagonist does not spare, then the fight continues, saying that it was "worth a try". continues to assault the protagonist with further attacks, and the Flavor Text proclaims that "The REAL battle begins." After the protagonist dodges all of his attacks,, in a desperate attempt to kill the protagonist, repetitively slams the protagonist's SOUL against the walls of the battle box, though the protagonist survives this. then uses his "special attack", which ends up being nothing (and thus never ends 's turn), as hopes that if nothing happens, the protagonist will quit out of boredom or simply remain trapped forever. However, eventually falls asleep, allowing the protagonist to push the box so that they can select the FIGHT option. dodges the first attack, but the second attack (unprovoked by the player) hits. He appears to bleed from his wound, though it's speculated by some to be ketchup. reminds the protagonist that he warned them before getting up, and weakly walking off-screen. Presumably hallucinating, he asks Papyrus (who is dead) if he would like anything at Grillby's. 's death grants the protagonist enough EXP to reach LV 20.

In Battle
See Sans/In Battle.

Protagonist
is the first monster the protagonist meets outside the Ruins. His attitude towards the protagonist is mostly dependent on their actions, though he usually enjoys pranking the protagonist and occasionally hanging out with them, unless they kill Papyrus. Near the end of the Neutral Route, he judges them depending on their actions. At the end of the True Pacifist Route, considers them a good friend.

initially considers the protagonist to be an "anomaly"; his intentions of befriending them was in hopes that they'd stop resetting the timeline. The only reason he doesn't kill the protagonist in Snowdin is because of a promise he made to Toriel.

Papyrus
cares for and admires his brother. He reads him bedtime stories, and gives him presents under the identity of Santa. Nonetheless, he likes to mess with him as he would with anyone else.

is worried about others hurting Papyrus or taking advantage of him. If the protagonist kills Papyrus, will resent them greatly and disappear for most of the game. On various endings, is afraid to tell Papyrus about other characters' deaths, so he lies about them going on a vacation.

Toriel
Toriel and are close friends, sharing a love of bad jokes; though they never see each other in person until the end of the True Pacifist Route, the Family Ending, or the Exiled Queen Ending.

While not being one to keep promises, complies with her request to not harm any human that passes through the door exiting the Ruins. At the end of the Genocide Route, he indirectly apologizes to her, as he is forced to break his promise to stop the protagonist.

Flowey
In one of the Neutral Endings, Flowey calls Sans "[Papyrus's] garbage brother" and "smiley trashbag". He says he tried to experiment with using his SAVE ability. However, "caused more than [his] fair share of resets" as if  was just about the only thing capable of stopping him, much like it is for the protagonist on the Genocide Route.

W. D. Gaster
There are a few things that hint a connection between and W. D. Gaster. These include the blueprints found in his workshop and the fact that the sprites used for his animations are labeled "gasterblaster".

Name
's name alludes the typeface in which he speaks in, Comic Sans. This is a reference to Helvetica, which is a webcomic about a skeleton named after a font. Papyrus and Comic Sans are both widely considered to be ugly and overused fonts. His name is also a pun due to his comical personality. The word "sans" means without.

If the player attempts to name the Fallen Child "", the game responds "nope." and prevents the name from being used.

Trivia

 * He is one of the three characters who will try to convince the player to stop playing the game, the others being Flowey and the Fallen Human.
 * He makes a brief appearance alongside Papyrus at the end of the Undertale Demo if the protagonist does a pacifist playthough.
 * , along with Undyne, are the only characters in the game witnessed playing an instrument, the former playing a trombone, and the latter playing a piano.
 * There is evidence to support the idea that is left-handed.
 * Sans greets the protagonist with a handshake using his left hand.
 * At Grillby's he holds and drinks the ketchup bottle with his left hand.
 * When riding the tricycle in the True Pacifist Ending Credits, he uses his left hand to steer it, while keeping his right hand in his jacket.
 * He uses his left hand when using gravity attacks in his boss fight.
 * may call the protagonist to ask if their fridge is running in Snowdin Forest.
 * Despite being a skeleton, 's hand doesn't resemble a skeleton's. This can be explained with him wearing gloves, as his hometown's climate is cold.
 * Killing Sans does not increase the protagonist's kill count.
 * If Papyrus was killed in a previous run, when the protagonist talks to on the bridge, he curtly tells them not to fight Papyrus.