Sans

Sans (/sænz/, SANZ) is the older brother of Papyrus and a major character in Undertale. He first appears in the forest after the protagonist exits the Ruins. He serves as a supporting character in the Neutral and True Pacifist Route and as the final boss and heroic antagonist in the Genocide Route.

Appearance
Sans is a short skeleton with a dimpled smile and large orbits. He wears an unzipped blue hoodie, a white t-shirt or sweater, black shorts with white stripes, and a pair of sneakers or slippers. He has white pupils that disappear when he is serious. When Sans uses magical psychokinesis, his left eye flashes light blue and yellow, and his right pupil disappears.

Personality
Sans is laid back, often sleeping on the job and taking breaks. His laziness is a combination of fatalism and apathy. He wonders if his indolence stems from his knowledge that any progress he makes will be erased when the timeline resets. Conversely, he suggests that this knowledge could be "a poor excuse for being lazy."

Though Sans is usually agreeable, he becomes eerily serious at particular moments. He is also observant; Sans reads the protagonist's expressions and can often tell when they have already done certain tasks. He enjoys making bad, skeleton-related puns; although the fact that he performs at MTT Resort hints that he may be a talented comedian. He enjoys science fiction and loves to drink ketchup. He also hates making promises.

Sans may have a scientific background. Evidence includes: the quantum physics book, workshop, his relationship to Alphys, affinity for science, and his timeline research.

Abilities
Sans can quickly travel using what he calls "shortcuts."

In battle, he uses "Gaster Blasters," devices that resemble a skull, to shoot a kind of laser beam. Sans excels in combat and fights with unique abilities that include: Karmic Retribution, changing the effect of gravity on the SOUL, and attacking the protagonist in the selection menus. His magic reacts to EXP; Karmic Retribution would presumably be weaker if the protagonist had little EXP.

Because of his research, he has knowledge of timelines and the SAVE function. However, he does not retain his memories when the protagonist loads a SAVE, and he cannot use the SAVE function. His awareness of time travel makes him scrupulous, and he recognizes when the protagonist is behaving unusually. Sans reads the protagonist's expression and determines if they have experienced events before and are repeating them. He also knows how much EXP the protagonist has and comments on it when judging them.

Sans also plays the trombone, though he is only seen playing it once. Papyrus finds his "incidental music" annoying, so he must play it on other occasions.

Like other characters, Sans is aware of when the game's code suffers bugs and calls the protagonist a "dirty hacker" if they achieve an impossible ending of a Neutral Route.

Neutral Route
Sans introduces himself to the protagonist in Snowdin Forest after he initially appears as a silhouette. He explains that he has no interest in capturing humans, but that his brother, Papyrus, does. Then, Sans hides the protagonist behind a lamp whose shape is identical to the protagonist's. Papyrus rushes onscreen, and the brothers discuss Sans's laziness and the importance of puzzle upkeep. Sans appears multiple times throughout Snowdin Forest, observing and commentating on the puzzles but not engaging in any japery, except for the word search.

Before Papyrus's battle, Sans is absent in Snowdin. He appears briefly to play trombone during the date/hangout with Papyrus, but will not appear again until the final corridor if the protagonist kills Papyrus.

After entering Waterfall, Sans is found manning a sentry station and asks the protagonist if they want to take a break with him. If the protagonist agrees, he takes them to Grillby's via "shortcut." The patrons warmly greet Sans, and he proceeds to treat the protagonist to a burger or fries. After some ketchup nonsense, a spotlight falls on him and the protagonist; time appears to stop as Sans tells the protagonist that a flower has been talking to Papyrus. Sans believes that someone is tricking Papyrus with an Echo Flower when the flower in question is Flowey. Sans can be seen again in Waterfall and pranks the protagonist with a red-eye telescope.

The protagonist passes him sleeping at a sentry post in Hotland when fleeing from Undyne. Undyne notices him sleeping and berates him mid-chase.

Later, Sans sells Hot Dogs in Hotland for 30G. If the protagonist attempts to buy a hot dog when their inventory is full, he stacks a maximum of 30 hot dogs on their head for free. These "head dogs" will vanish when the protagonist enters the next room.

Further on, Sans waits outside of MTT Resort and asks the protagonist if they want to grab a bite to eat. He escorts the protagonist inside via "shortcut" and talks about a woman he has befriended that shares his affinity for puns. He tells the protagonist that this woman made him promise to protect any human that left the Ruins and that, if she had not said anything, the protagonist would be "dead where [they] stand." He dismisses this as a joke immediately afterwards and says that he has done a great job protecting the protagonist. If the protagonist has not died before, Sans takes credit for their success. If the protagonist has died, Sans will question the validity of his statement. Before leaving, he tells the protagonist to take care of themselves because someone really cares about them.

Judgement
The protagonist encounters Sans for the last time in the final corridor. He explains that EXP and LOVE are acronyms - "EXecution Points" and "Level Of ViolencE" - and judges the protagonist for their current EXP.
 * If the protagonist gained no EXP, Sans will begin to talk normally and will skip his judgment, 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.
 * TundraBasement.png the protagonist restarts from a SAVE Point after hearing his speech or has completed the Neutral Route before, Sans 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 Sans gives them the key to his room.
 * If the protagonist gains some EXP, Sans will allow them a moment to think of 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, Sans judges the protagonist based on how high their LV is:
 * If the protagonist is at LV 1 but has more than 0 EXP, Sans presumes that they killed someone just to see what he would say about it. He says " wow. you're a pretty gross person, huh? "
 * If the protagonist is at LV 2, Sans says that it is pretty sad that the protagonist messed up the slightest amount, and that they probably did not know what they were doing, but then says that he is kidding, stating: " who gets to LV 2 on accident? get outta here. "
 * If the protagonist is at LV 3, Sans gives the protagonist a C+ and tells them that they can do better.
 * If the protagonist is above LV 3, Sans says that they probably killed some people on purpose, though maybe some of it were in self-defense, and that he is not sure, as he was not watching.
 * If the protagonist is above LV 9, Sans says that does not 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, Sans 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 resets again after hearing his judgment, Sans will comment that the protagonist still looks bored and that they should " consider our session over. "
 * If the protagonist killed Papyrus, Sans goes on to tell the protagonist that he suspects they have some 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 will not 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, Sans 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
Sans will be absent from the final corridor in the true pacifist route. There is also no SAVE point or box upon entering the hall.

Sans 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. Sans, along with the protagonist's other friends, are bound by Flowey, yet still protect the protagonist against Flowey's attacks. However, Sans is absorbed by Flowey, along with all the other monsters and their souls.

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

After defeating Asriel, Sans 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. Sans 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, Sans exits the Underground and heads to the Surface along with the other monsters.

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

In the credits, Sans 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
Sans stalks and introduces himself to the protagonist as usual but requests that they continue pretending to be a human. He does not comment on the protagonist turning around before he asks them to. Sans goes along with Papyrus's japery and does not appear as an NPC as he does on other routes. After the protagonist crosses the bridge before Snowdin Town, Sans warns them not to fight his brother or else they will "have a bad time." He then disappears and is absent until the final corridor.

If the protagonist aborts the Genocide Route by sparing Papyrus, Sans 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 is no one left in Snowdin. Alternatively, it is implied that Sans follows the protagonist if they kill Papyrus. In the final corridor, Sans 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 not to take another step forward. After the protagonist takes another step, Sans engages a fight against the protagonist and apologizes to Toriel for breaking his promise.

After a short monologue, Sans begins an onslaught of attacks against the protagonist as he contemplates why he can no longer watch the protagonist from afar. After he finishes his initial speech, Sans offers to spare the protagonist and tells them that accepting will make his job a lot easier.

If the protagonist spares him, he tells them that he will not let the protagonist's choice to give up on the route go to waste. He then kills them or "dunks them," as he puts it, with an unavoidable attack and asks them not to return on the game over screen. If the protagonist returns, Sans's appends his second attempt to convince the protagonist to stop fighting. When the protagonist attacks him, he says that means they never really were friends and asks the protagonist not to tell other instances of Sans in other timelines.

If the protagonist does not spare Sans, the fight continues, and Sans comments that the protagonist likes to do things the hard way. After this choice, the flavor text proclaims that "The REAL battle finally begins." After the protagonist dodges all of his attacks, Sans repetitively slams the protagonist's SOUL against the walls of the battle box 36 times. Though the protagonist loses 1 HP each slam, the HP does not decrement after reaching 1. Sans then uses his "special attack,": absolutely nothing. Sans says that, if nothing happens, the protagonist will quit out of boredom or remain trapped forever.

However, Sans eventually falls asleep, allowing the protagonist to push the bullet board so that they can select the FIGHT option. Other options are unavailable, and the box can only be pushed towards the fight button. Sans dodges the first attack and begins to speak when the protagonist kills him using a second attack, which is unprovoked by the player. He appears to bleed from his wound though it is speculated to be either ketchup or an injection of liquid determination. Sans reminds the protagonist that he warned them before he slowly stands up and walks off-screen. Presumably hallucinating, he asks the late Papyrus if he would like anything from Grillby's.

The death/spare sound is played, and the protagonist's EXP is set to 99999, granting them LV 20 (regardless of their EXP before the encounter – in normal playthroughs, it will always be 50000). If the player resets after killing Sans and fights him again, Sans notices a disturbing look on the protagonist's face and states that he " won't grace it with a description. " He becomes more disturbed by the protagonist's expression if he is killed and re-fought repeatedly.

Sans does not count as a kill in the Stats menu, and the game does not record whether or not he is killed. Because of this, the player can skip Sans's battle by changing the protagonist's room from 231 (room_sanscorridor) to 232 (room_castle_finalshoehorn) in their save file.

In Battle
See Sans/In Battle.

Protagonist
Sans 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, Sans considers them a good friend.

Sans initially considers the protagonist to be an "anomaly"; his intentions of befriending them were in hopes that they would stop resetting the timeline. The only reason he does not kill the protagonist in Snowdin is because of a promise he made to Toriel.

Papyrus
Sans cares a lot 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. (example from Papyrus date, when Papyrus says " A JEALOUS TROLL HAS BESIEGED MY ONLINE PERSONA, ALWAYS SENDING ME BAD PUNS IN A GOOFY FONT. ")

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

In the Genocide Route, Sans will also warn you not to kill Papyrus. His eyes disappear showing that he is dead serious and afterward disappears entirely, expecting the protagonist to comply.

Toriel
Toriel and Sans 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.

In the Exiled Queen Ending, Sans becomes Toriel's roommate if Papyrus has been killed. In this route, Sans also states that he "can't bear to tell her what (the protagonist) did."

If Papyrus was not killed, Sans and Papyrus visit Toriel often, play board games together, and sometimes convince Toriel to leave the Ruins.

While not being one to keep promises, Sans complies with her request to watch over and protect 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 Sans using his SAVE ability. However, Sans "caused more than [his] fair share of resets," as if Sans was just about the only thing capable of stopping him, much like it is for the protagonist on the Genocide Route.

Alphys
It is hinted that Sans and Alphys have a history, possibly working under W. D. Gaster. Just before heading to the surface in the Pacifist Route, Alphys jokes that everyone has been fighting for the ability to watch anime on the Internet, as does Sans. She jinxes him and says she knew he would make the joke. Papyrus inquires as to how they know each other. Alphys stutters ineffectually before Sans covers for her.

W. D. Gaster
There are a few things that hint a connection between Sans and W. D. Gaster. These include the blueprints found in his workshop and the veiled machine, the sprites used for his skull-like laser gun attacks are labeled gasterblaster, and his knowledge of the "anomaly" eventually causing the destruction of the world in a Genocide Route.

Trivia

 * Sans's name alludes to the typefaces in which he speaks in: Comic Sans and Sans Serif. This is a reference to Helvetica, a webcomic about a skeleton named after a font.
 * Papyrus also has this allusion, considering he always speaks in Papyrus's typeface.
 * In Japanese phonetics, Sans's name is homophonous with the name of the Sanzu River, a boundary between death and the afterlife in Buddhist lore which, like Sans, judges all who cross it for their deeds. The Sanzu River is also a recurring locale in the Touhou series, from which Toby drew inspiration for Undertale ' s bullet hell battles.
 * His name is also a pun because he enjoys many types of jokes and serves as comedic relief during his initial encounter.
 * "Sans" means without.
 * If the player attempts to name the Fallen Child "Sans," the game responds " nope. " and prevents the name from being used.
 * He makes an appearance alongside Papyrus at the end of the Undertale Demo if the protagonist gained no EXP.
 * Sans and Undyne are the only characters known to play an instrument: trombone and piano, respectively.
 * Sans appears to be left-handed. Evidence includes:
 * Greeting the protagonist with a handshake using his left hand.
 * Holding and drinking a ketchup bottle with his left hand while dining at Grillby's.
 * Steering a tricycle using his left hand in the True Pacifist Credits.
 * Manipulating gravity with his left hand in his battle.
 * When the "fun" value is between 45 and 50, Sans calls the protagonist in Snowdin Forest to ask if their fridge is running.
 * Despite claiming to be a skeleton, Sans's hand does not resemble a skeleton's. Similar to his brother, Sans may be wearing gloves even though skeletons do not get cold.
 * Killing Sans does not increase the protagonist's kill count.
 * There is a glitch in which Sans will walk up off the screen at Grillby's when he takes the protagonist there. His dialogue will still appear normally.
 * Sans is the only character that dies off-screen. This leaves the Schrodinger's cat effect for players.
 * Sans's Lost Soul's dialogue is displayed in the usual font (instead of Comic Sans) and sways back and forth.