Sans

Sans is the brother of Papyrus and a major character in Undertale. He first appears in Snowdin Forest after the protagonist exits the Ruins. He is the deuteragonist of the Neutral and True Pacifist routes, in which he keeps an eye on the protagonist throughout the game. He is also the final boss and heroic antagonist of the Genocide Route, in which he confronts the human in the last corridor.

Sans appears as a relatively short and paunchy skeleton, with mitten-like hands. Sans is always seen with a wide, toothy-grin on his face. Sans wears a blue hoodie, a white t-shirt underneath, black shorts with white stripes, and a pair of slippers. He has white dots in black eye sockets that disappear when he is serious or angered. When Sans uses telekinesis, his left eye flashes light blue and yellow (the colors for patience and justice) while his right pupil vanishes.

Sans is lazy, often sleeping on the job and taking breaks. His laziness is a combination of fatalism and apathy, as he is aware of timeline resets. Conversely, he suggests that this knowledge could be "a poor excuse for being lazy."

Waterfall location Sans telescope Sans's fake telescope. He enjoys being mischievous. Sans primarily acts this way towards those he is in good terms with. His antics range from an assortment of illogical, juvenile, and slightly inconvenient pranks. Examples include Sans "selling fried snow," using whoopee cushions, sharing an unscrewed ketchup bottle, and eye paint on a telescope. He is not above utilizing his teleportation or other magic for practical jokes either. Sans is also fond of making the occasional low-brow puns. He enjoys making others laugh in general, as he also performs at the MTT Resort as a comedian. Despite Sans being apathetic towards his own life, he is considerate to those he cares for. For example, Sans is a regular at Grillby's, and the monsters and Royal Guard dogs treat him kindly. Sans has informed Big Mouth about "all kinds of incredible foods," yet Big Mouth comments that "he always orders the worst burger off the menu." Although Sans hates making promises, he respects Toriel's request to watch out for any humans. Even if the protagonist killed people that were close to him, Sans refrains from broaching the topic until the Last Corridor. In a Neutral Route ending where Papyrus or Toriel is alive, Sans omits the protagonist's slaughter to either of them. He is also observant; Sans reads the protagonist's expressions and can often tell when they have already done certain tasks. Though Sans is usually agreeable, he can become eerily serious to emphasize a subject. Regardless of the human being partially or wholly merciful, Sans tells them that if "the old lady" (confirmed in the True Pacifist Route to be Toriel) had not made him promise to protect them, "(they'd) be dead where (they) stand." During the Genocide Route, he does everything in his power to kill the protagonist, even faking mercy. Sans may have a scientific background. Evidence includes the quantum physics book, his workshop, affinity for science, his inexplicable ability to teleport and his timeline research. Sans has implied he once longed and searched for a life that he cannot go back to as he "gave up trying to go back a long time ago". As a Lost Soul, he tells the protagonist that "you'll never see 'em again." Although what Sans is trying to return to is vague.

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 Town. He appears briefly to play trombone during the date/hangout with Papyrus but does not appear again until the Last 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 a "shortcut." The patrons warmly greet Sans, and he proceeds to treat the protagonist to a burger or fries. After some dialogue, a spotlight falls on him and the protagonist and 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. Later, if Papyrus was killed, "a hooded figure" watches Shyren's battle. However, if Papyrus was spared, Sans sells concert tickets made of toilet paper, implying the other figure was Sans as well. The protagonist passes him sleeping at a sentry post in Hotland if the protagonist flees from Undyne. Undyne notices him sleeping and berates him mid-chase. Sans does not appear in this spot if Undyne was killed, even if Papyrus was spared. 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. Further on, Sans waits outside of the 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 (implied, and later confirmed to be Toriel) 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 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 questions the validity of his statement. Before leaving, he tells the protagonist to take care of themself because someone really cares about them.

The protagonist encounters Sans for the last time in the Last 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 skips his judgment, instead praising the protagonist for embracing compassion and actively choosing to be merciful to the monsters throughout their journey. He reinforces the idea that the protagonist's actions shall decide the fate of the world in one of two ways: the protagonist lets Asgore take their SOUL and allow the monsters to break the Barrier, or they take Asgore's SOUL to escape the Barrier themself. Impressed by their feat, Sans concludes that the protagonist now has enough determination and believes that they can do the right thing before leaving. Papyrus and Sans's House location workshop. Sans's workshop entrance is located behind his house. If the protagonist has heard his speech before, Sans notices their bored expression and offers a secret codeword that he uses to prove that they are a time traveler. After the protagonist loads their SAVE a few times, Sans's suspicions are affirmed and he gives them a key to his room. Inside Sans's room is a key to his workshop. If the protagonist gained EXP, Sans allows them a moment to think about their actions. He then emphasizes the importance of integrity and, if Papyrus is alive, concludes that whatever happens next is up to the protagonist. If the protagonist killed Papyrus, Sans expresses his suspicion that they have some special power. He then asks if the protagonist thinks it is their responsibility to do the right thing. Regardless of their answer, Sans reminds the protagonist of his fallen brother and leaves. If the protagonist returns to the Last Corridor after loading a SAVE, Sans judges the protagonist on their earned LV. Subsequent attempts to talk to Sans after judgment prompts him to tell the protagonist to "consider [their] session over."

In the neutral route, after the protagonist defeats Photoshop Flowey, Sans calls and informs them of the events that transpired after their departure. The content of this phone call varies depending on the protagonist's actions.

In the pacifist route, sans is absent from the Last Corridor in the True Pacifist Route. However, he does appear during the pre-Asriel cutscene and meets Toriel face-to-face for the first time. Flowey binds Sans and the protagonist's other friends, then eventually absorbs their SOULs after they defend the protagonist from Flowey. During the battle against Asriel, Sans appears as one of the Lost Souls alongside Papyrus. 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 because Toriel's thumbs are too big for the phone buttons. When the protagonist is ready to leave, Sans exits the Underground and heads to the Surface along with the other monsters. When Papyrus runs off to introduce himself to the humans, Sans says that someone must keep him away from trouble and runs off in the opposite direction, presumably to use a "shortcut." In the credits, Sans rides a tricycle on a highway and overtakes Papyrus's sports car, much to his brother's annoyance.

In 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 Last Corridor. If the protagonist aborts the Genocide Route by sparing Papyrus, Sans reappears at the Waterfall sentry station and expresses his respect for their mercy to Papyrus. He continues to appear as he does on the Neutral Route but does not take the protagonist to Grillby's since Snowdin has been evacuated. Sans screenshot before battle. Sans's Last Corridor speech in the Genocide Route. After killing Papyrus, the protagonist continues to kill all the monsters in the Underground. Sans watches them secretly without confronting them directly, hoping they would heed his friendly advice and stop. Eventually, he decides to stop them himself no matter what. Sans confronts the protagonist in the Last Corridor but does not judge, instead claiming they must have been busy. He starts off by paraphrasing one of Papyrus' statements. Instead of answering, the protagonist takes a step forward. Next Sans laughs and asks "do you wanna have a bad time?", threatening them with force should they proceed. When the protagonist dismisses his warnings and continue to advance, he fights them. Before the battle begins, Sans apologizes to the late Toriel for breaking his promise to her. Sans repeatedly dodges the protagonist's attempts to hit him and retaliates with his relentless attacks, doing his best to stop them. When he approaches exhaustion, he decides to stall forever by doing nothing, and refuses to let the protagonist have their turn, hoping they will eventually quit of boredom. Sans however falls asleep, giving the protagonist a window of opportunity without his interference. When they manage to attack again, Sans dodges once more, but fails to avoid the second, and takes a whopping 9999999 damage. Recognizing his failure, Sans makes one desperate attempt to deter the protagonist, and slowly walks out of the screen while joking that he is going to Grillby's. He then speaks to his dead brother, asking him if he wants anything, and disintegrates shortly after.

Sans is the final boss of the Genocide Route. Similar to the Neutral and Pacifist routes, he waits for the protagonist at the Last Corridor. However, he skips LOVE judgement, apologizes to Toriel, and begins an encounter. Sans alters the SOUL Mode to Red or Blue, and uses White and Light Blue Attack Types. He uses various complex bone patterns, straight beams from "Gaster Blasters," and telekinesis. Excluding telekinesis, Sans's attacks inflicts KARMA, a mechanic that dwindles the protagonist's HP. Excluding the first attack, Sans sets the SOUL to Blue mode for the first half of the battle. At the halfway point, Sans also occasionally swaps to Red mode, or uses a mix of Red and Blue. Sans's attack style is focused on platforming, spontaneity, and forcing quick decisions. Sans always attacks first at the start of the battle.

To progress the fight, the protagonist must keep attacking Sans, as checking reveals that he cannot dodge forever; performing any other action besides FIGHT, including skipping/missing the attacks, does not progress the battle, as his dialogue does not appear or advance. Sans does not attack the protagonist when he attempts to offer false mercy, which allows the protagonist to heal as many times as they need to. After getting past his mercy offer, the fight then includes Sans constantly flickering the screen as he transitions through his attacks, uses his "Gaster Blasters" more often, and even attacks the protagonist as they navigate the menu (though menu attacks only deplete their HP to 1 and cannot kill them). After enough turns, Sans then performs an attack lasting roughly 40 seconds, launching some attacks shown previously at the protagonist, including a large array of bones, a bevy of "Gaster Blasters", and many slams against the Bullet Board's walls (the protagonist's HP is depleted by 1 for every slam but stops once their HP reaches 1, preventing the attack from killing them). Once the protagonist survives his final attack, Sans uses his "special attack," where he stalls indefinitely, preventing the protagonist from accessing the menu, in hopes for them to withdraw out of boredom. The protagonist must wait until he falls asleep, then slowly push the Bullet Board to the left and then downwards so they could access the "FIGHT" option while Sans does not notice them. The Bullet Board cannot be pushed elsewhere, and should they try it too early, Sans will wake up and his eye flashes as he teleports the protagonist's SOUL back to the middle. When the protagonist's SOUL hits the FIGHT option, they attack Sans. He wakes up and dodges it, only to be defeated by another attack that does 9999999 damage. Sans does not perish immediately, but starts to leak a red fluid of some sort. He warns the protagonist one final time, then limps off-screen before his presumed death, raising the protagonist's LOVE to 20 and HP to 99.

Sans dodges up to 24 attacks, thus negating his need for high defense or health. Through KR, Sans drains the protagonist's HP by 1 per frame, and can inflict multiple weak hits (up to 30) at a rapid rate. The amount of KR inflicted varies per attack type, and its duration is based on how much the SOUL was hit. This dwindling effect is also active during the protagonist's turn. However, the protagonist cannot be killed until KR's effect ends. The exception is if the SOUL gets damaged near the end of their HP during one of San's KR inflicting attacks. Notably, the protagonist's INV can slow down the effects of KARMA. Some attacks involve rectangle platforms, which is green on top, and is white on the bottom. These can be seen outside of the Bullet Board. The SOUL can jump through the white portions of these platforms and rest on top of one. After Sans pretends to spare the protagonist, he also attacks with bones on the action menu. These bones deal 1 damage per hit, does not inflict KR, and cannot kill the protagonist.