Sans

Sans is one of the main characters in Undertale. He is Papyrus's older brother and lives in a snowy town called Snowdin. His role in the game is to become either a friend or an enemy of the player, depending on the choices they make. His only confrontation in the game is during the Genocide Route.

Sans is a very charismatic and distinctive character, known for breaking the fourth wall and being aware of how many times we restart the game. He's known for making really bad jokes and being one of the most mysterious characters in the game.

Sans is a short skeleton with a slight weight problem.

He has a large head with round eyes. His pupils are white, but they disappear when he speaks in a serious or threatening tone. He always wears a smile due to the shape of his skull. He only slightly moves the corners of his mouth when he speaks, while he uses some kind of magic or telekinesis to produce the sounds of what he says. In battle, he emits a bright, flashing iris in his left eye that flickers between blue and yellow.

Being a walking skeleton, he cannot make many facial expressions, but he is able to move with enormous fluidity and perform attacks enhanced with telekinesis.

Sans wears an unbuttoned blue hoodie at all times. He wears black shorts with a white stripe down the center and pink slippers. He also wears a white undershirt beneath his blue jacket.

As a detail; the bony shape of its missing nose is shaped like an upside-down heart.

Sans is a guy with a lazy and relaxed attitude. He often falls asleep at work and takes frequent breaks.

Sans is portrayed as a popular guy who loves telling bad skeleton jokes, which constantly annoy his brother. He performs as a comedian at the MTT Resort, because even though he's aware his jokes are really bad, he has a great talent for comedy.

At first glance, he seems like a nice, friendly guy. He always maintains a relaxed attitude that is often comforting and unique to others. He's rarely seen angry or sad, as he rarely reacts in any particular way. However, he becomes eerily serious when he feels truly threatened, bordering on being annoying. This is shown when he confesses to Frisk that if it hadn't been for the promise he made to Toriel, he would have died right there. Sans often says that he doesn't like making promises.

Sans is quite observant, and also very lazy. He's aware of how many times he's defeated the player and how many times the game has been reset, which makes his laziness a mix of apathy and denial. He's somewhat unsure if being aware of the game resets has broken his spirit, knowing that everything he does will be pointless, since even if they manage to reach the surface, they'll just return to the Underground again. Possibly also an excellent excuse for being lazy.

Sans is extremely mischievous, he often puts fart pillows in his hand and shakes it with others, he also often unscrews the salt and ketchup bottle to ruin other people's food, even selling hot cats (A parody of hot dogs).

Sans possesses knowledge of multiple timelines through the SAVE function, as he has a hidden laboratory behind his house where he records scientific experiments, though he himself cannot use the SAVE option to save the game. Some of his memories are lost after a RESET, though he can recognize when the player has performed one.

• Sans has the ability to move incredibly fast and teleport using "shortcuts" to get anywhere.

• During the final battle, he can fire a kind of beam using a weapon called the "Gaster Blaster." The Gaster Blaster, whose name means "Gaster's weapon" or "a weapon against Gaster," bears a resemblance to the DT Extraction Machine found in the True Lab, Gyftrot's head, and the head of Asriel Dreemurr's final form.

• Sans can also tell if the protagonist has achieved an impossible ending on a Neutral Route, by calling him a "dirty hacker" in the final phone call.

• Sans also knows how to play the trombone, although he is only seen using it once.

• On one occasion, Sans can be seen combing his hair, obviously a joke about him not having hair because he is a skeleton.

Frisk: Sans is the first monster she encounters upon leaving the Ruins. At the end of the True Pacifist Route, Sans considers Frisk a good and great friend, but in the Genocide Route, he sees her as a heartless monster.

His intentions in maintaining a friendship are good, as it is to try to stop the anomaly.

Papyrus: Despite his lazy attitude and bad jokes, Sans admires and cares deeply for his brother Papyrus. Papyrus has a huge obsession with the human house, as he always dreams of being a royal and popular guard. He reads his brother bedtime stories and helped him make his battle suit a few weeks before Frisk fell into the Underground. He also likes to tease him from time to time by telling one of his bad jokes.

Sans is very worried that other people will take advantage of Papyrus's innocence.

Unlike Sans, Papyrus is a taller and more flexible skeleton.

Asgore: Asgore is Asriel's father and Toriel's ex-husband. He has a similar appearance to Toriel and is the king of the Underground.

Undyne: Frisk speaks to Undyne for the first time during their initial battle encounters. After being chased by Undyne, Frisk collapses from the heat, and since Undyne's body is similar to a fish's, Frisk quickly takes advantage of the situation to give her water. Frisk visits Undyne at Papyrus's house, where Papyrus helps them become best friends, revealing more of Undyne's mischievous personality and even setting the house on fire in the process. When Undyne finally decides to fight Frisk to regain her honor as a royal knight, she realizes that Frisk is a "weak loser with a big heart," just like Asgore, and decides to befriend them. After Frisk's date with Alphys, she begins to fix and improve upon her past mistakes.

Flowey: Flowey is considered the only villain with malicious intentions. He experiments on Sans using his SAVE ability, but it has no effect because Sans is aware of each reset, implying that Sans has been the only person capable of stopping him, just like Frisk in the Genocide Route.

Alphys: She is portrayed as a short scientist with many social insecurities regarding her love of anime and her admiration for Frisk, spying on him and helping him in any way she can.

• There are many clues that demonstrate that Sans may have had a scientific background; his work area, his dialogue in his boss fight in the Genocide Route, the quantum physics book in his house, the mysterious machine, Papyrus mentioning his passion for science fiction (especially if it is real), among others.

• "Sans" is a preposition that means without anything.

• If you enter Sans's room, his bed can be seen in a state of disrepair, making it unsuitable for sleeping (with the bedspread rolled into a ball and the pillow tossed aside without a cover), which could explain why he falls asleep in various parts of the game. He also owns a treadmill that he uses to prank the player upon entering his room, though Papyrus claims he's just playing a joke across space and time.

Sans is one of the three characters who will try to convince the player not to continue playing the Genocide Route; Flowey and Undyne are the other two. However, if you follow the Genocide Route twice, Chara will tell you to take another path.

• Sans has the ability to teleport, although it is also believed to be some kind of super speed.

• Near Snowdin, in the hallway towards the mysterious door, Sans seems to teleport from one side of the screen to the other and jokingly asks the player if they are following him.
In the Genocide Route, he sometimes teleports visibly, such as when he warns the player in a bad moment before entering the town of Snowdin.

• Sans loves to drink ketchup, as can be seen in his interaction with the player at Grillby's, where he won't eat his portion of the food but will drink the entire bottle of ketchup if refused.

In the Snowdin forest, if you examine their lookout post near the ruins, you will reveal a number of bottles of various condiments inside.

This is why, after the fight with Sans in the Genocide Route, Sans is the only monster seen "bleeding" in the game. There's a belief that, because he consumes entire bottles of ketchup, he ends up "bleeding" ketchup from his wounds.
Sans's blood could also be due to the fact that bones contain traces of blood. This is a possibility, as Sans wouldn't be any different from any other skeleton.

Despite that, Papyrus doesn't bleed, and just turns to dust like any other monster.

• It's possible to kill Sans multiple times by reloading a previous save, which will result in extra dialogue. "...That expression you've got... You're a real freak, aren't you?"

Although the death counter does not increase, this possibly implies that Sans never truly dies.

• Despite appearing to have a cheerful and playful personality, Sans is very serious and calculating, as can be seen in several more serious parts of the game and outside of it.

• By going to the Laboratory and calling Papyrus on his phone, he will say that Sans loves science, so he would maintain some connection between him and science.

• In Japanese phonetics, Sans's name is a homophone for the Sanzu River, a boundary between death and the afterlife in Buddhist tradition that, like Sans, judges all who cross it by their deeds. The Sanzu River is also a recurring location in the Touhou series, from which Toby drew inspiration for the hellish battles in Undertale.

• If we do the pacifist route without saving the game and lose against Asgore, Sans will give us the key to his room when we talk to him again, jokingly saying that he must learn the truth and that Frisk deciphered the triple-secret code. As soon as she sees it, he already has the key in his pocket, due to Sans's speed.
After wandering for quite a while through a strange, empty place, Papyrus appears in the doorway, revealing that Frisk was simply using a walking machine in the dark. After some dialogue, a kind of tornado of trash can be seen in a corner. After taking another key from his drawer and noticing how messy Sans is, we have to go behind the house. There we find a secret room with a broken and damaged machine (possibly a time machine), and also a picture of Sans with other people, looking happy. There are also some emblems and blueprints in unreadable symbols, which seem to have something to do with the machine. (There's a strange machine behind the curtain; it looks broken...)

Origin of Sans: It is said that Sans was a human who lived on the surface, because at the end of the True Pacifist Route, his brother Papyrus asks him, looking at the sunset, "What's that yellow ball?" referring to the sun. Sans replies, "We call that the sun, my friend." Their statement implies that Sans already knew about the surface and had been there, and it seems Papyrus already knew he had been there. The theory states that Sans simply came from another game, "Earth Bound," in a Hack Room where Ness and his three friends enter a time-warping machine. Inside, they try to return to their correct timeline, but without Ness, who has disappeared without explanation. From this, it could be said that Sans is a Ness who got lost in time and space. One of the vendors in Snowin tells Frisk that one day he and Papyrus simply appeared and sat down together there. However, Sans tells the player that he sincerely wishes he could go home, but he gave up on returning a long time ago, and that going to the surface no longer matters to him or simply doesn't fulfill or attract him, which is why he says he comes from the surface. When he mentions that he can control time and timelines, he implies that he comes from another time, which explains what happened to Ness with the time warp machine. This explains why Sans appeared in the Underground so suddenly and why he knows about timelines. In the secret lab behind his house, there are more clues, such as a photo he took with three friends whom Frisk can't recognize—the same three friends Ness had—along with some blueprints with illegible handwriting, which are likely from the Mr. Satunds family due to their poor spelling. Another drawer contains a medal, possibly the one Ness wore, and finally, behind the curtains, there's a machine, possibly the phase warper he arrived with.

However, if we have restarted the game several times, we will see that the photo he had with his friends is now a poorly drawn picture with a note that says; "Don't forget..." Implying that although the restarts affect him, he can never forget that he was once happy, although on other occasions he seems to remember nothing but a few exceptions.

It is well known that Asgore harbors great resentment and contempt for humans, which is why he proclaimed the law to kill any human who fell into the Underground. Although nothing is known about the previous human souls, it is theorized that they were all cared for by Toriel, and that Sans did not kill them because he promised Toriel that he would not kill any child who passed through there; hence the dialogue: "That's why I hate promises." which Sans says in the Genocide Route.

The aquamarine soul is patience, the third soul is orange representing courage, the fourth soul is that of a dark blue girl representing integrity, the fifth soul is violet representing perseverance, the eighth soul is green with the gift of kindness, and the seventh is light yellow representing bravery.

Chara strongly hates humans, possibly due to some mistreatment she suffered.

Chara is the name of Asgore and Toriel's daughter, who feeds on Frisk's body when they kill a monster.

Despite appearing on the surface in Deltarune, it can be seen that it is another timeline.

Before Sans arrived in town and Frisk fell into the Underground, Sans mentions that he used to frequent the Snowin Forest and knew someone who understood and laughed at his jokes, even though they were terrible. He never saw her face, as they spoke through a door. This person was possibly Toriel, who promised him that she wouldn't kill any humans and that she would protect anyone who passed through that same door with her life. One day, he found her sad and withdrawn. Sans hated promises, but he couldn't break them to the only person he loved and who understood his jokes. After that, he never spoke to her again.

"The easiest enemy. Can only take 1 damage."