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I wouldn't call him lazy, though. Sure, he slacks off... But he handles public speeches, he goes scouting for the queen. He manages the Canine Unit, and he's always just... there. And unlike me, he's not afraid to stick up for what he believes in.
Alphys, Part 27B

Sans is PAPYRUS' older brother and a supporting character in Inverted Fate. He is lieutenant of the Royal Guard and the final boss in Snowdin, but remains a recurring character throughout the story.



Papyrus made the outfit Sans usually wears. It consists of a neatly wrapped, blue scarf with stripes, blue mittens, a short-sleeved blue jacket with a  Delta Rune badge, blue boots, and a white shirt with the Starman emblem.

However, he switches from this outfit to a golden suit of armor early in the comic, though he keeps the vest, scarf, and boots. Said armor bears the Delta Rune Emblem, emphasizing his royal guard status.


Laid back, social, loves bad puns and pulling pranks. Seems to know just about everyone in the underground and can comfortably chat it out with just about anyone. He’s got a keen eye– excellent observation skills. Like his canon self, he is incredibly good at picking up on expressions and can deduce a lot by reading faces. For as much as he presents himself as a pun-loving lazybones, he’s very sharp, and there’s a lot going through his head at any given time.

The thing is, while he’d love to laze around and do nothing, he’s not actually as lazy as Papyrus claims. As a royal guard, he takes his jurisdiction over Snowdin very seriously and genuinely cares about keeping it a safe, comfortable environment for the monsters there. He also does a lot of scouting, thanks to his teleports. In fact, they’re part of the reason he can get away with all those breaks and naps– because usually it only takes a short time for him to scout.  What’s more, he uses the lazy schtick to his own advantage; by appearing as this friendly slacker, it means any legit threat would underestimate him. They wouldn’t expect a guy like him to be packing Gaster Blasters and other nasty tricks.

Misdirection’s a handy technique. He was brought up with the understanding that humans have, can, and WILL overpower monsters if they aren’t careful. And even if they are, there’s a distinct power imbalance. Enough hate, and poof. So he fights smart, bends the rules. His guard training’s given him the strength to fight hard, but even so, he’d rather fight smart, if at all.

However, much of Sans’ feelings remain under lock and key. His worries for his brother, any regrets for abandoning his dream, certain tragedies all but forgotten, the dread that another human might come and what that would MEAN, given what he knows about Tori’s thoughts on the matter, and given recent public revelations. The royal guard’s become less about providing a defense and more about an offense when that final human arrives. The people are desperate for freedom, putting pressure on him, on Alphys, and especially Toriel. And now a human’s here, and his bro’s befriended them, and to top it all off, they’re both keeping secrets. It’s stressful, to say the least.

And, truth is, he’s kinda cynical. He just hides it behind humor and an unwavering smile. He’d rather lighten the mood, keep people happy. His brother especially. Just about everything he does is for Papyrus’ sake, and he puts him even above his status as lieutenant. For as much as he hates promises and commitment, he’ll throw that all aside for his brother’s sake, though at the same time, his position forces him to take a more realistic than idealistic approach. He WANTS to believe in Papyrus, wants to believe they can work things out peacefully, but experience has taught him that it’s just not that simple, and sometimes you have to take what you can get. He’s made plenty of compromises he wasn’t happy with.


Sans grew up in the capital alongside his brother and father, Dr. W.D. Gaster. In his teenage years, he worked alongside his pops, hoping to one day follow in his footsteps. A grand announcement was made about the unveiling of a new and exciting invention. One that would revolutionize the sciences and the lives of monsters everywhere.

The machine was one that would tap into the powers of a monster SOUL, rebirthing them into something greater and stronger. But disaster struck. During their first field test, the power overloaded, red alerts activated, and the CORE was at huge risk of meltdown. Despite the grave danger, Gaster refused to exit the machine, and Sans was left with a decision. Risk the CORE exploding on the small chance the machine works...
... or lose his father for all others to walk away safe. He chose the second option, firing a Gaster Blaster at the machine, saving the CORE but losing his father.

It was on the outskirts of town that he met Undyne, a plucky young monster who bombarded him with questions. Ultimately, he found her antics amusing enough to distract from his grief, and in time he took her in as an apprentice, while circumstances thrust him into the position of Royal Scientist at the young age of 15[1].

Naturally, this was a stressful time in his life. He and his brother were just orphaned, and to top it all off, Pap was just a small child. Nonetheless, Sans attempted to continue where his pops left off, though in the end he could never fix the machine, and eventually the pressure coupled with his guilt and grief made him hang up his lab coat.

Then, one day, he abruptly decided to try out for the royal guard. He never explained why, not even to his brother. For a new beginning , he moseyed down to the dump for the guard tryouts and wowed both Toriel and Gerson with a flashy display of Gaster Blasters. He was accepted as a trainee just like that and soon formed a friendship with his fellow trainee, Alphys. Over the years, the two would train together, climbing the ranks of the royal guard side by side.

When it came time for Gerson to retire, he turned to Sans as his successor, but Sans ultimately turned the offer down in favor of Alphys, partly due to her hard work and partly because absolute leadership was too much for him[2]. Still, he'd act as Alphys' right-hand man, handling a lot of the more social aspects of the guard while commanding the Canine Unit.

All the while, his brother took up the sciences in his stead, and while Sans was proud of Papyrus' efforts, he couldn't help but wonder if he was really happy following in his footsteps. Still, he showed support to the best of his abilities, but when the DT experiments began to take a turn for the worst, it carved a rift between him and Undyne that remains even to this day[3]. In fact, he grew so suspicious that he asked Mettaton to look out for Papyrus and keep a close eye on Undyne, just as an added precaution.[4]

Main Story

Snowdin Arc

Sans first appeared part 5B of the comic, having spotted Papyrus off by his invisibility device, alongside a human. However, Papyrus had already taken a shine to the kid, introducing complications from the start[5]. And while Sans tried to keep a cautious distance, their love of bad puns and friendship with Papyrus slowly but surely won Sans over[6]. Despite his efforts, he started to care. And that was kind of a problem.

Because apparently three teenage delinquents saw the human use “scary human powers”. And because, apparently, some suspicious flower had befriended both the kid and his brother, and Papyrus refused to tell him their plans[7]. And because, APPARENTLY, Undyne had seen the kid, as she tampered with one of Snowdin’s puzzles from afar, upping the danger and nearly getting Papyrus hurt in the process[8]. Sans managed to reprogram it at the last second and even gave Undyne an earful over the phone[9].

But she was set in her plans, which forced Sans’ hand.


When the kid reached Snowdin Town, he’d invite them to stay with him and Papyrus. Ease them in. Get them nice and cozy, so they’d never wanna leave[10]. And at first, they had a ball, but a MTT news report soon revealed that the teens had gone all the way to Undyne. Footage of Frisk’s face appeared on the airwaves. Now everyone would know who they were[11].

Worse yet, Papyrus and Frisk clearly had plans to leave Snowdin. Papyrus insisted they had another way to bring happiness to everyone, but he just wouldn’t say why. It was as if he trusted the flower more than his own brother.

Sans, frustrated, tried to keep it cool over the course of the night, but based on his observations, he chose to take the cautious route and wait on the edge of town. Sure enough, the kid showed up, but the moment they saw Sans, they instantly reloaded, bringing Sans back to his room with a nagging deja-vu[12].

This happened again and again, each time increasing the strength of Sans’ deja-vu until, after several loads and nagging suspicion, Sans cut the kid off before they left the house. They had a short chat, and he even offered them some pie from Toriel. He then waited by their side, faking sleep, and when they left, he immediately pursued.

But this time, he had a strong feeling that something would happen. Just as Frisk reloaded, he used his shortcuts to warp to Papyrus’ location, safe from the effects of any time tomfoolery.

They talked, discussing the matter, and ultimately decided to follow Frisk together. Retaining his memory of that last loop, it was clear that the kid had done SOMETHING, but there was no time to dwell on it, as Frisk entered Grillby’s, surrounded by drunken monsters, and Sans hastily diffused the situation.

He told them to meet on the edge of town for a serious talk, and when Frisk and Papyrus arrived, he was frank with them. Venturing beyond Snowdin risked getting caught by the rest of the guard, who were far less merciful than he was. The only way to leave the Underground was to take Toriel’s SOUL, which he just couldn’t allow. All in all, they were better off staying put, especially with Pap refusing to share his secrets.

But Frisk and Papyrus refused to turn back, and so a fight ensued.


Sans used this opportunity to prove a point, using his variety of bone and gravity-related skills to beat Frisk down. While Papyrus tried reasoning with him, Sans refused to budge, and it wasn’t long before Frisk was wiped out, allowing Sans to drop them in the pocket dimension Papyrus had made just for him. A chance for the kid to cool off[13].

But Frisk left soon enough, and they and Papyrus fought again. And again. Each time growing more desperate. Papyrus started using his magic to support the kiddo, and Frisk even attempted to flirt to diffuse the situation. But while the two certainly worked well as a team, the risks seemed too great. He continued to beat Frisk down, but each time, they came back more determined than ever. It reached a point where Sans opted to use his “special attack…”

Trapping Frisk in a turn, unable to do anything but wait it out. In the cold. Until they just gave up.

But Papyrus pleaded one more time. He and Sans talked it out, Sans assuring Papyrus that this was best. Frisk could live a happy life until they died of old age. Then the monsters could leave peacefully. Wasn’t that for the best? But Papyrus disagreed, viewing such treatment as imprisonment. Snowdin was small, after all. Moreover, Papyrus would never bring a human into danger unless he was certain it would be worth it.

Didn’t Sans believe in him…?[14]

At that point, Sans couldn’t take it anymore. His own brother questioning his belief was the last straw.

He didn’t understand, but the kid had more than proven themself, and Papyrus clearly had some kinda agenda in mind. So, reluctantly, Sans offered to play dumb, suggesting they take the Riverperson’s boat past Fort Aquarius in order to bypass the Royal Guard altogether.

But before the duo left, Papyrus wound up roping both Sans and Frisk into a “date” of sorts, even creating a wacky gizmo to generate a visual novel type interface for them to share.


Badly dubbed anime antics and over the top dating sim shenanigans ensued, and though Papyrus had hoped for romance, in the end, neither Frisk nor Sans took it seriously. One, Sans was way too old, and two, Frisk’s flirting was just for fun anyway. But they had a good laugh, and after Sans and Papyrus provided Frisk with a disguise, it was time to part ways[15][16].

Waterfall/Fort Aquarius Arc

Believing at first that they had taken the boat, Sans met with Alphys in Waterfall, where he covered for the kid by claiming they had worn him down and snuck off. She didn’t seem fully convinced, and though he tried to encourage her not to let Undyne get to her, his words fell on deaf ears[17].

Their meeting concluded when Sans mentioned the suspicious flower, asking her to keep her eyes peeled just in case.

After that, he took it relatively easy, though a nagging suspicion ate at him. What if the Riverperson wasn’t there? What if something went wrong? At first, he opted to just call Mettaton, who confirmed his suspicions by mentioning a power outage at the Fort. And while Sans, like with Alphys, warned MTT about the flower, before booking it to Fort Aquarius[18].

Sure enough, MTT was right. The guard was on high alert. Apparently someone had broken in, hacking the power grid. Knight Knight, one of the higher ranking guards, had even been imprisoned in one of the empty cells… for a time.


Fearing the worst, Sans high tailed it to the roof just in time to find his brother and Frisk facing off with the fort’s leading sergeant, Dohj. And though they had worn her down and provided a great photo op by triggering her canine instincts, it wasn’t long before she began questioning Sans’ motives. He’d intended to take Frisk and Papyrus into “custody” for his own personal questioning, but the fort was under her jurisdiction[19].

As more guards assembled, the situation got worse and worse. They were told to join Sans in bringing the human to Alphys. If he did anything rash, it’d completely blow his cover. Even Alphys arrived before long.

Luckily, Papyrus was smart enough to whip up a smokescreen and escape with Frisk in tow. But after the ruckus died down, Alphys berated Sans for lying to him, allowing the kid to leave Snowdin, and bringing stressful complications.

But he didn’t care about duty and responsibility if it meant doing the right thing for the kid and his bro. And he knew, deep down, Alphys felt the same way. Besides, even if the worst came to pass, humanity probably wouldn’t look kindly upon them, and Alphys would have to prepare for the worst.

Before leaving her, he reminded her of her position of Captain- at the end of the day, she was boss. She could make a stand for what she believed in.

But the rest was up to her, along with Frisk and his bro.

In the end, all seemed to work out, though, as Papyrus and Frisk eventually broke through Alphys’ facade. As she left in shame, Sans reappeared, urging them to go meet with her. He even teleported them into her house, where Papyrus set up an impromptu party[20].

At first Alphys didn’t take it well, but after some coaxing from Sans, she eventually agreed to let them stay. He left for a time, giving them space, but at the end, when all seemed smoothed out, he made a return to offer some extra encouragement and, when Frisk and Papyrus left, he stayed by her side as added company[21].

Hotland Arc

He left only twice. First to attend the fighting tournament put on by MTT in Hotland, where Undyne made a fool of herself in his eyes by continuing to cling to her violent fixation on claiming the final SOUL at the cost of her friendship with Papyrus [22][23].

After the tourney, he returned to try and coax Alphys into joining him at the televised trial, but after watching Undyne have a meltdown on live TV, the poor Captain grew even more fearful of speaking her mind, forcing Sans to once again take matters into his own hands[24].


Thus, Sans appeared as a witness in the trial, bringing the Snowman along for the ride[25]. His goal? To shift suspicion from Frisk to that shady flower that had been chilling with the kid and his brother the whole time. This shift in focus stunned the crowd and left Undyne furious, but Sans' evidence was fairly damning. Strange seeds at the scene of the crime? An eyewitness?

Unfortunately, Undyne shifted the focus back to Frisk by bringing up Fort Aquarius, thus Sans' plan screeched to a halt. In the lobby, he bickered with Undyne, calling out her plans as child murder, but took a back seat for the next chunk of the proceedings and only occasionally weighing in during Dohj's testimony. By the time Frisk, Papyrus, and Undyne had taken their toll on the canine sergeant, Sans took his chance to leap back into action and once again put pressure on Flowey[26].

His testimonies were airtight, with further evidence against Flowey, from photographs of strange cracks in the floorboards to vine cuttings from Fort Aquarius and even security footage showing the little weed. Ultimately, he concluded that Flowey was the one pushing Frisk and Papyrus to infiltrate the fort, thus the blame fell upon his nonexistent shoulders. Unfortunately, this testimony not only left Undyne deeply hurt and angered, but it stressed Papyrus out due to his desire to keep Flowey's intentions secret. Ultimately, Mettaton opted for a surprise "plot twist" to conclude the trial, leaving Flowey's fate up in the air. Thus Sans departed for New Home to take matters into his own hands.



At the Throne room, he briefly met with Toriel and tried to plead Frisk's good nature at the very least, but she refused to meet with another human, leaving Sans not only with Flowey to tend to, but once again forced him to act as a roadblock to both the kid and his brother[27].

Soon enough, Frisk had arrived with Papyrus, with the former running away from the latter quite stressed and mortified over their actions. Sans realized that they hadn't saved since their battle with Undyne and that things would end sour if they went to confront Toriel in this state. He again brought Flowey into the subject, stating that if he really was their friend, he'd comfort Frisk instead of pushing them forward. His words fell on deaf ears as Frisk attempted to move past him. That didn't work. Sans stood his ground and made sure he kept them in place by fighting. Although rather than attacking them directly, he only made sure to harm them if they were to ever try moving forward as he and Papyrus try to talk to Frisk.

Eventually, the two brothers helped Frisk realize that they weren't in the right state of mind. However, they break down over their failures as they cried while stating themselves to be a screw up. Sans then had a heart to heart moment with Frisk by hugging them and saying that despite everything that's happened over the course of their adventure, they still kept going even without hurting anybody as Papyrus joins in the hug as well.

They both encouraged Frisk to "go back" and set things right. Sans, however, warned them both that things still could backfire. He also stated that he should fight them since it was his job, but doesn't and tells Frisk a code word: "I am the Legendary Fart Master". Papyrus was clearly annoyed, but Sans told then it would come in handy later on before Frisk reloads.

After reloading,Frisk was able to confront Undyne earlier by encouraging Mettaton to go and escort Papyrus. Together, the three of them were able to move past this without anyone getting too injured. Mettaton stayed behind to tend to Undyne as Papyrus and Frisk headed to New Home.

New Home & Loose Ends Arc

While Frisk and Papyrus ventured through New Home, they encountered Sans in the corridor once more. As the latter again begins to monologue over their actions, Frisk interrupted him by stating the codeword. With his suspicions confirmed, Sans realized it wasn't the first time this has happened and allowed the duo to pass, while stating he should apologize to Alphys. Before leaving, Sans questioned Papyrus if they should really trust Flowey. Even though his brother confirms that he can, Sans remained doubtful and told them to stay wary. He then abruptly left the corridor through a shortcut.

When Papyrus and Frisk finally confront Toriel at the barrier, she refuses to listen to their plan and separates Papyrus from the two of them with a cage of fire. With no other way to help, Papyrus runs off to receive assistance. It is only after a short while when he finds his older brother and, while on the phone, asks if he could do anything to help. Sans gives a sarcastic response by asking if he looked like a fire elemental. Papyrus then deduces that they go help Frisk in person and tells the latter to keep standing their ground.

Sans and Papyrus arrive at the barrier just as the fight ends and Flowey hands Toriel the Mage's soul after she loses it.After checking on Toriel, Sans then asks Toriel if Flowey caused any harm, only for the Queen to defend the flower by saying he kept the Mage's soul safe. Flowey then accuses Sans of painting him as a villain, saying that if he really was evil, he would've killed Toriel. Papyrus stands by his creation and says that deep down, he is hurting like Toriel.Sans refuses to respond and offers to escort the Queen back to her home. Toriel entrusts Frisk, Papyrus and Flowey with the human SOULs and leaves with Sans in tow.

Victory Arc

In the Final Interlude, Sans stands alone looking at the CORE, talking about how he grew out of wishful thinking after Gaster went overboard with his experiments and he's not too sure about current events. Frisk and Papyrus appear, asking him why he's just sulking near the CORE. Sans says he's just looking back before monsters escape to the surface. Papyrus argues that he never looks at the CORE but goes off-topic to present the Golden Pineapple, which Frisk asks what that has to do with anything, answered by Papyrus saying he and Sans made a bet that Sans would come clean should Papyrus and a human ever bring him a golden pineapple.
Sans jokes about the history of golden pineapples, but then finally confesses his history with Gaster, his brief time as Royal Scientist, and why he joined the Royal Guard to Papyrus. After he's done, Papyrus asks why Sans kept it all a secret for so long, and Sans admits it was probably just pride and looking back on bad memories. Frisk and Papyrus march on to the elevator, before stopping to return to Snowdin.



  • Sans' voice contains a deep Western accent, based off of the fact that in the Japanese version of Undertale, he uses the pronoun "oira" (おいら); which is to evoke a person with a rural background, a "country bumpkin".


Main Cast FloweyFriskCharaPAPYRUSAsgore DreemurrNapstablookSansAlphysMad Mew MewMettatonUndyneToriel
Ruins DummyRuins Bullies
Snowdin Dogamy and DogaressaDoggoLesser DogGreater DogSnowdin TrioSnowmanJerryMonster Kid
Waterfall Bassiere von Dohj IIIKnight KnightMadjickRG 01 and RG 02GersonMasaSpout WassarBratty and Catty
Hotland RG 03 and RG 04GlydeSo SorryParsnikAstigmatismMigospelMisyrmMuffetBurgerpants
The CORE Robot 98Robot 100The Season Dudes
True Lab MechamalgamatesMemoryheads
Other Characters Fallen humans (The Mage) • LilacW.D. GasterSpamton