History Characters / UndertaleSans

* VideoGameCrueltyPunishment: He will judge you near the end of your journey, and he has some [[PlayerPunch choice words]] should you engage in VideoGameCrueltyPotential. [[spoiler:And if you've been going for the Genocide Route, he bars your path as ''the'' single toughest boss in the game.]]

* TheUnfought: You never fight Sans on a Neutral run, especially if you have aborted the [[spoiler:Genocide route]]. [[Spoiler:Downplayed and implied in True Pacifist as a lost soul. He is forced to "fight" the player in this state, but while it is hard to tell ingame, only Papyrus's bone attacks appear onscreen, indicating that Sans doesn't even bother to attack you.]]

* WalkingSpoiler: There's quite a bit more to Sans than just the joke-loving skeleton you meet early on. Those avoiding spoilers take heed: even glancing at fanart of Sans will almost certainly give away something about his character. And, y'know, there are many {{spoiler}} marks here for a reason. [[spoiler:To sum up, Sans is one of the two {{Fourth Wall Observer}}s, '''the''' FinalBoss of the Genocide Route plus [[CombatPragmatist how he fights]], and the fact [[IWarnedYou he warns you if you win]] that it's the PointOfNoReturn.]]

[[Characters/UndertaleOtherCharacters Minor]] | [[Characters/UndertaleMonsterEncounters Monsters]] | [[Characters/UndertaleSpoilerCharacters Spoilers]] ([[Characters/UndertaleTheFallenHuman The Fallen Human]])]]]]

* BewareTheSillyOnes: Inverted trope, as he's a non-villainous example. While Sans tells bad skeleton puns and is incredibly lazy, [[spoiler:he can provide quite the ass-kicking when someone sets him off]].

* AllPowerfulBystander: [[spoiler: Deconstructed. Because of his MediumAwareness, Sans is one of ''the'' most powerful monsters in the Underground, but that same awareness is what keeps him from fighting harder to either save or leave the Underground. He knows full well that everything will end up being reset thanks to your (and Flowey's) SaveScumming, and thus no longer sees the point in trying; from his perspective, there's not much point to doing anything ''but'' standing by. He doesn't even attempt to stop you from killing ''his own brother'' because he knows that will eventually be undone as well (that being said, he also won't forgive you for doing it). He will only get involved at the end of the No Mercy route, by which point he's basically the only one left who ''can'' get involved, because the protagonist was left alone to murder everything in their path.]]

* ArmorPiercingAttack: Yes, he can only deal 1 damage, but he also [[{{Reconstruction}} reconstructs]] ScratchDamage into this. [[spoiler:When you fight him in No Mercy, the fact that his attacks hit you ''per frame'' while leaving DamageOverTime makes your recently acquired ArmorOfInvincibility absolutely ''useless''.]]

* BadassBoast: He gives several such boasts before and during [[spoiler:his boss fight]]:
-->'''Sans:''' heh heh heh heh...all right. well, here's a better question. [[DontMakeMeDestroyYou do you wanna have a bad time?]] 'cause if you take another step forward...you are REALLY not going to like what happens next.
** He gives this one right before your battle with him:
--->'''Sans:''' it's a beautiful day outside. birds are singing, flowers are blooming. on days like these, kids like you... [[spoiler:'''[[LetsGetDangerous Should be burning in hell]]'''.]]

--->'''Sans:''' hmm. that expression...that's the expression of someone [[spoiler:who's died thrice in a row]]. ''[{{beat}}]'' hey, what comes after "thrice," anyway? [[PrepareToDie wanna help me find out?]]

* BeginWithAFinisher: When you fight him in No Mercy, he opens with his strongest attack right away: [[spoiler:a combination of GravityScrew, SpikesOfDoom, and BeamSpam with WaveMotionGun]]. Sans lampshades his usage of the trope:
-->'''Sans:''' huh. always wondered why people never use their strongest attack first.

* BewareTheNiceOnes: An extremely chill and amiable guy, Sans is liked by everyone who knows him (except [[TheSociopath Flowey]], obviously) and treats you like an old friend mere seconds after you meet him. It usually takes a ''lot'' of effort to get Sans legitimately angry with you, but if you do... at best, [[spoiler:[[WhatTheHellPlayer he'll call you out for the dirty scumbag you are]]]], and at worst, [[spoiler:''say your prayers and hope it's over quickly'']].

-->'''Sans:''' geeettttttt dunked on!!

* BossCorridor: The [[ExactlyWhatItSaysOnTheTin Last Corridor]] is completely empty until Sans suddenly appears and stops you in your tracks. Subverted in that he does not fight you, but he does assess your actions and deliver judgment, including some well-deserved {{Player Punch}}es if you screwed up. [[spoiler:Double subverted if you go on the No Mercy route, where he decides to actually step into the fray and gives you one hell of a fight.]]

* CatchPhrase: On a No Mercy run, before fighting Papyrus, he tells you that if you keep this up, "you're gonna have a bad time". [[spoiler:He repeats the line again at the Judgement Hall as a BadassBoast, and the line is used in his fight by the battle text.]]

* ChekhovsGunman: He seems like a simple joker at first — though he can be a bit scary early on in the No Mercy run — but as you find out later, he is the ''only'' reason you were able to make it as far as you did. In fact, he's been helping you all along — after all, what would a sentry from Snowdin be doing outside of his station, selling items that just so happen to help raise your health?

* CombatPragmatist: He pulls just about every dirty trick in the book, and constantly breaks the rules of the combat system to compensate for his low stats. Some examples include [[BeginWithAFinisher launching a powerful attack right at the start of the battle]], dodging attacks, ignoring MercyInvincibility, and hitting you ''during menu selection''. In his second phase, he's also able to change attack patterns on the fly just to screw with you. On the first and every subsequent time you reload after being defeated by him, he also gains the ability to randomly interrupt his own opening speech to catch you off-guard with his first attack. He tries [[BreakThemByTalking breaking the player character by talking]], and even pulls an ISurrenderSuckers before delivering a OneHitKill.
-->'''Sans:''' huh. always wondered why people never use their strongest attack first.

* DeadlyHug: While the game implies that Sans "hugs" the child to death in the English release should you accept his offer, he outright states this in the Japanese localisation instead:
--> "Huh? You died? That's weird. All I did was try to hug you..."

** Another happens at the end of No Mercy, where he turns the conventions of Turn-Based [=RPGs=] on their head. [[spoiler:He ''starts'' the fight with his strongest attack, powerful enough to waste you within moments. He plays into the expectation that every boss battle has that BattleIntro — only to ''[[TalkToTheFist skip]]'' said intro to sucker-punch you. You may have 99 ATK, but there's no Dodge stat in this game, meaning there's nothing that says he can't just sidestep your attacks. And he knows that Scratch Damage will ''hurt'', even against 99 DEF, [[DeathOfAThousandCuts when done a lot, with added poison effect]]. Then he starts to outright cheat by not letting you have your turn in peace, attacking you while it's your turn. And this is all before his space/time bending abilities, tricking you into {{Smash Cut}}s after Smash Cuts.]] Needless to say, this makes for a ''very'' difficult battle.

* TheDreaded: Anybody who successfully invokes Sans's wrath learns to fear him. Flowey states in a post-Neutral conversation that [[spoiler:Sans is the only thing that has kept him from reaching Asgore on his No Mercy runs, and he's had to reset multiple times to avoid him; the only time Flowey gets the better of him is in the True Pacifist run by catching him and everyone else off-guard]]. [[spoiler:The Fallen Child, despite expressing nothing but contempt and confidence during the rest of Genocide Run, will [[OOCIsSeriousBusiness express concern]] only when they have to fight Sans.]]

--->[[spoiler:''He can't keep dodging forever.'']]

** He is '''''really''''' lazy, even if the cause of that is debatable. While it's played for laughs every time it comes up for the most part, [[spoiler:he winds up exhausted should the player make it all the way to the end of his final barrage in No Mercy. From there, he starts to doze off...]]

* TheFatalist: His humorous façade hides a deep and bitter cynicism. He stopped caring a long time ago and prefers to observe, rather than act. [[spoiler:However, he eventually gets motivated to take a stand near the end of the No Mercy run, despite acknowledging that due to your ability to reset, it's impossible for him to really win. The most he can hope for is to get you to RageQuit.]]

* FinalBoss: Of the [[spoiler:No Mercy]] route. After him, [[PostFinalBoss you move on to Asgore]], [[spoiler:[[ZeroEffortBoss who's automatically one-shotted]], so he's the last true boss you'll fight]].

* ForgivenessRequiresDeath: If you accept his offer of friendship in No Mercy Run: [[spoiler:"If we're really friends.... you won't come back."]]

* TheFourthWallWillNotProtectYou: He's ''really'' showing it in No Mercy. [[spoiler:A lot of his boss fight mechanics are designed to screw you, the player playing the game, instead of the in-universe character. Of particular notes are him skipping his BattleIntro straight into an AlphaStrike, throwing attacks at your cursor browsing the menu, and his ultimate attack of doing nothing so you never get your turn to end the battle. He also refers to you, the player, as 'The Anomaly', and outright tells you his HiddenDepths and calling out your actions across the game.]]
* FragileSpeedster: Sans is [[spoiler:a OneHitPointWonder]], but is skilled at dodging and makes very rapid attacks with his magic. Good luck getting even one hit in.

* GenocideBackfire: His fight at the end of the No Mercy Run can be interpreted as this. He is the toughest boss of the entire game and has brought many players to just give up, but he will actually never fight the player in any other timeline but the one where you literally kill everyone in the Underground.

** Amusingly, they both have different opinions on Let's Players and their audience. [[spoiler:In the No Mercy run, Flowey calls the audience of Let's Players cowards and sickos for wanting to watch the Genocide route without doing it themselves. In the Neutral and Pacifist routes, specifically on the Xbox edition [[MakesJustAsMuchSenseInContext inside Papyrus' sink]], Sans, ever the lazybones, asks why you wouldn't just watch a video of the "exclusive [Xbox] game" instead of playing it yourself.]]
* GoodIsNotSoft: Although Sans is a genuinely nice guy and almost always acts it, [[spoiler:he was apparently completely prepared to murder you the moment you stepped out of the Ruins if not for a promise. While his implied motivation for doing so — ridding the world of the creature that he believes is the cause of the time anomaly his world is stuck in — was clearly good (and, in many runs, completely justified), it still speaks volumes that he was willing to stone-cold murder a child in order to achieve it]]. And, if you kill enough people to make him [[spoiler:intervene and fight you]], he treats you absolutely ''ruthlessly''; with the exact same smug-as-hell attitude he always has, [[spoiler:he insults you, mocks you, torments you with deliberately-unfair attacks, cheats, lies, rubs his own power in your face — whatever it takes to discourage you enough that you stop playing, since he knows that's the only way he can possibly save everybody at this point]].

* HopelessBossFight: His battle in the No Mercy run is this. [[spoiler:Not for you, but for ''him''.]] While he can (and will) kill you very quickly and messily, [[spoiler:he knows it won't do any good since you can just reload your save and try again, and it's only a matter of time before you finally defeat him. The best he can hope for is to try to get you to RageQuit from the difficulty]].

** Also, if the player attempts a No Mercy, Sans echos something that [[spoiler:Asgore]] says on Neutral and Pacifist runs when they met the protagonist, but of course with a different meaning.

* LaserGuidedKarma: While fighting him, your life bar is under a "KR" effect that [[spoiler:slowly decreases your HP like poison every time Sans hits you]]. Given cut battle narration lines in the script stating you're doomed by KARMA, many speculate that KR stands for Karmic Retribution. He also attempts to kill you [[spoiler:by feigning a truce]], much like you easily could have done for Toriel and many ordinary monsters at this point.
-->''"You felt your sins crawling on your back."''

* LetsGetDangerous: In the No Mercy run, he comes to realize he can't stand by anymore, and resolves to finally do something to stop you.

* ManChild: Not nearly to the extent of his brother, but he definitely has shades. On top of having a very goofy sense of humor, his work ethic, cleaning habits, and general lifestyle are all reminiscent of a lazy, irresponsible teenager. Unlike Papyrus, however, this has a lot less to do with his actual maturity level and lot more to do with him [[spoiler:having [[StoppedCaring very little motivation in life to do much of anything]] due to a ''lot'' of unresolved emotional baggage]].

* NiceGuy: [[SurprisinglyCreepyMoment Occasional creepy moments aside]], he's very friendly and always treats the player like an old buddy, even after they just met. [[spoiler:Makes sense after all, he's well aware that this most likely is not the first time he's met the player; him befriending them is his way to make a potentially genocidal player think twice about going through with it. He has his limits, however: kill his brother and he'll want nothing to do with the player, only appearing again to tell them off at the end of the game. Probably the only reason why he doesn't make them have a bad time then and there after killing Papyrus out of rage is because the player can still reset the timeline, thus undoing his battle/murder.]]
* NightmareFace: A subtle example: if he's threatening you or being very serious with you, the shine in his eye sockets vanishes, which makes him look less like a friendly cartoon skull and more like, well, a talking dead person.

* ObfuscatingStupidity: Sans appears to be a regular goofball — [[spoiler:unless you take the No Mercy route, where he threatens you and challenges the player to an ''extremely difficult'' boss battle]]. In addition, the contents of his workshop and his {{Offscreen Teleportation}}s imply he's a quantum physicist with a working time machine, who has a working knowledge and connection with the space-time continuum in-game.

* OptionalBoss: Zigzagged. [[spoiler:Sans ''is'' required to finish a No Mercy run, but the No Mercy run itself is ''not'' required ([[VideoGameCrueltyPunishment nor is it recommended]]) to get True Pacifist or even Neutral. Just getting to Sans requires killing every monster in the Underground, which is easier said than done due to the increasingly sporadic random encounters and [[UpgradedBoss Undyne the Undying]]. By contrast, Omega Flowey and Asriel are much more straightforward with how they're fought, and both have to be beaten to achieve True Pacifist.]]
* OrphanedSetup: Due to coding error, some of his [[HaveANiceDeath lines]] [[spoiler:from No Mercy]] in the earlier versions of the game didn't have the intended punchline, as below (the missing parts are in bold).

** He'll count how many times [[spoiler:you've died to him on the No Mercy path]], with a snarky comment for each one of the first eleven attempts. [[spoiler:Only after 12 deaths in a row will he stop coming up with unique lines.]]

** Alluded to when facing him as a Lost Soul, and explicitly stated [[spoiler:when fighting him on a No Mercy run]]. His knowledge of [[spoiler:the player's and Flowey's interference with the timeline (through saving and resetting), and the belief that things will inevitably be reset again in the future]], has left him exhausted and existentially depressed. It's implied that this also has something to do with the strange machine Sans is working on...

* StrongerSibling: Ambiguous. On paper, Papyrus has significantly higher stats than Sans, but then again, on paper, everyone has higher stats than Sans, "the easiest enemy". [[spoiler:But Sans has an enormous arsenal of attacks, including {{Wave Motion Gun}}s, access to [[DamageOverTime Karmic Retribution]], the ability to [[FragileSpeedster dodge]], and the ability to InterfaceScrew the player to hell and back, making him potentially the [[WeakButSkilled more skilled sibling]] if not the stronger one.]] However, it is left ambiguous whether Papyrus lacks Sans's capabilities, or simply the [[CombatPragmatist combat pragmatism]] to use them in a fight. [[spoiler:If the player stops a previously No Mercy run on Papyrus, his dialogue implies that he may have access to [[WaveMotionGun Gaster Blasters]], yet he never displays them in a battle.]]

* ThisLooksLikeAJobForAquaman: His stats are the worst of any monster in the game, ''including a literal child'', and he can only deal 1 damage to the player with each attack. Howevever, [[spoiler:his [[DamageOverTime special ability]] being called [[{{Karma}} KR]] seems to imply that he is specifically effective against the player at the end of the No Mercy Run ''[[CreateYourOwnHero because]]'' of all the LOVE collected before fighting him]].
* ThresholdGuardian: He blocks your path in the Final Corridor, and will judge you for all you have done across the game. If you pass with flying colors, he will basically say 'nice work'. If you've been engaging in VideoGameCrueltyPotential, especially if you kill Papyrus, he has some PlayerPunch to deliver. If you've been violent without going into outright KickTheDog territory, he basically leaves you to judge yourself unless you press the issue. [[spoiler:And if you've been going for the No Mercy route, he gets off his ass to stop you '' personally.'']]

** ''"You'd be dead where you stand."'' - referencing that if Toriel hadn't asked him [[spoiler:to leave you be, he would've instantly killed you the moment he saw you.]]
** [[spoiler:''"LOVE, too, is an acronym. It stands for '''Level of Violence'''."'']] - Near the end of the game, Sans reveals that [[spoiler:the EXP and LV stats]] refer to something ''much'' different than in other games. [[spoiler:EXP stands for "execution points" and quantifies the pain you've inflicted on monsters, while LV/LOVE stands for "Level of Violence" and measures how easy it is to kill them]]. The one hint of this being the case happens early in the game and is easy to miss, so Sans spelling it out at the end can easily come out of left field.
** [[spoiler:''"if you keep going the way you are now... you're gonna have a bad time."'']] - Said on the No Mercy run, in place of what was previously innocuous advice about the upcoming battle with Papyrus. [[spoiler:The screen then quickly cuts to black and back, and Sans is gone when the view of Snowdin returns. This is the only time in the game Sans is seen teleporting on-screen; every other time, he goes offscreen and ends up somewhere he shouldn't be able to reach from the direction he went.]]
** ''"what? you think i'm just gonna stand there and take it?"'' [[spoiler:Upon dodging the one-hit kill strike that felled so many bosses beforehand.]]

* WouldHurtAChild: Claims he would've killed you the moment he first saw you were it not for [[spoiler:his promise to Toriel]], and on a No Mercy run [[spoiler:he will do ''his very damnedest'' to break the promise]].
-->'''Sans:''' it's a beautiful day outside. birds are singing, flowers are blooming. on days like these, kids like you... [[spoiler:'''Should be burning in hell.''']]

* YankTheDogsChain: In a No Mercy run, he reveals that his apathy stems from a fear of this trope, because [[spoiler:he knows that any happy ending can be undone by the player resetting]].

** [[AlmightyJanitor Sans]] appears to be extremely knowledgeable about almost everything that goes on in the game, but [[LazyBum spends all his time loafing around]] and [[PungeonMaster making puns]] for his own amusement. [[spoiler:It is heavily implied that Sans is some form of time traveler/scientist that has observed multiple timelines. The reason he's so lazy is that [[CosmicHorrorStory he knows the truth about how easily the world can be reset regardless of what he does]]. Only on the [[ApocalypseHow Genocide Route]], where the VillainProtagonist becomes a threat [[EvilOnlyHasToWinOnce not just to that timeline but all of them]], does [[NeutralNoLonger Sans actually become motivated enough to fight]], and he's by far the hardest boss in the game.]]

** Taken to the next level if you kill him and reload the game to before his fight. No matter what, he ''has'' to fight you. And he still points out the savagery lightheartedly.

* ItsPersonalWithTheDragon: [[spoiler:Any player who plays a No Mercy run only to fight Sans apply this trope on him by default.]]

* BreakoutCharacter: Easily ''Undertale''[='=]s most iconic character despite his role being smaller than more than half the main cast's on paper. [[spoiler:His boss fight, theme, and lines in the Genocide Route led him to being so iconic]] that he ended up being the first ''Undertale'' character to make any sort of appearance in ''VideoGame/SuperSmashBros'', and even people on the internet who haven't played ''Undertale'' will likely recognize him.

** While Flowey has been pushed to being one, Sans has a lot of icon power on the internet, to the point where people who have only glanced at ''Undertale'' but never played it can probably recognize what game he's from when they see him elsewhere. Tends to happen when you're one of the most liked characters [[spoiler:and a freakishly difficult and memorable boss]].

* BreakoutCharacter: Easily one of ''Undertale''[='=]s most iconic characters despite his role being smaller than more than half the main cast's on paper. [[spoiler:His boss fight, theme, and lines in the Genocide Route led him to being so iconic]] that he ended up being the first ''Undertale'' character to make any sort of appearance in ''VideoGame/SuperSmashBros'', and even people on the internet who haven't played ''Undertale'' will likely recognize him.

%%Feel free to expand upon this page. Just know that's rife with spoilers

* AllPowerfulBystander: [[DownplayedTrope Downplayed.]] [[spoiler:He seems to be more powerful than everyone else in the underground]], and stays away from fighting because of his laziness [[spoiler:and how he knows that the world will just get reset anyway no matter what]], though unlike everyone else, he's also fully aware that [[spoiler:you are still so much more powerful than him due to your determination that fighting you is a HopelessBossFight. This is deconstructed, however, as due to the fact he does not make the decision to fight except in the worst possible timeline, he allows the player to get away with murdering monsters (including his own brother) despite the fact that if he took a stand earlier on, he'd probably be far more successful. This is due to him being aware of the Reset feature and realising that no matter what the player does, it will always be reversed at some point, 'except' in the No Mercy Run, where the destruction of the universe permanently alters the game's files.]]
* AlphaStrike: Sans does not mess around on the Genocide Route. His first attack is a strong contender for being his most powerful — a brutal gauntlet of [[spoiler:GravityScrew, SpikesOfDoom, and BeamSpam using [[WaveMotionGun Wave Motion Guns]] that can and most likely will waste you within seconds]]. [[spoiler:To top it all off, [[NoFairCheating he's also the only enemy in the game that gets the first turn]].]]

* HoistByHisOwnPetard: After an entire fight of throwing InterfaceScrew after InterfaceScrew at you, you beat his 'special attack' — [[spoiler:i.e. him refusing to make his next move so you can never take your turn]] — by breaking the interface yourself, allowing you to [[spoiler:press the Attack button in spite of it not being your turn. When even that doesn't work, The Fallen Child says "fuck it" and hijacks control from you to finish the job]].

* LazyBum: [[ZigZaggedTrope Zigzagged]], despite being one of his most obvious character traits. While in most runs, he's so apathetic as to be barely mobile, he puts more effort into stopping you than anyone but Undyne on [[spoiler:a Genocide run]]. It's also implied that [[spoiler:he busted his ass in the past to try and solve his world's problems through time and space before he realized it was simply impossible]], resulting in his current depressed, hopeless state. That being said, he admits that he might just be using depression as an excuse for his faults, and his lack of energy ends up [[spoiler:killing him regardless when he falls asleep, allowing the player to finish him off]].

* WeakButSkilled: Technically speaking, he really is the weakest enemy in the game, having only 1 HP and only capable of doing 1 damage. He makes up for it through clever abuse of game mechanics. [[spoiler:He only has 1 HP, but he dodges all of your attacks instead of just taking them like every other monster in the game. His 1-damage attacks don't trigger the MercyInvincibility, so he does 1 damage ''per frame''. That's not even getting into his [[ISurrenderSuckers SPARE trick]], or his "special attack". Indeed, the only reason you can even kill him is by breaking the rules yourself — dragging your SOUL over to the ATTACK button ''during his turn.'']]

* NoSell: Sans' battle is designed so that none of your equipment will give you an edge — [[spoiler:not even the [[InfinityPlusOneSword Real Knife]] or [[ArmorOfInvincibility the Locket]] — as he dodges every one of your immensely powerful attacks and pierces your defense via DeathOfAThousandCuts. You ''can'' still get healing boosts from the Burnt Pan and Stained Apron or gain a slight few MercyInvincibility frames from the Torn Notebook and Cloudy Glasses, but it doesn't count for much.]]

* {{Superboss}}: [[spoiler:Sans' fight is completely optional on most runs, and getting to him takes a lot of time and patience required to kill everyone in the Underground. However, once you meet the criteria for his fight, he's easily the hardest boss in the entire game with his attacks doing one damage per frame, said frames causing DamageOverTime, and an assortment of quick attack patterns that include [[WaveMotionGun Gaster Blasters]], his brother's [[GravityScrew Blue Attack]], and [[CameraScrew messing with your screen]] for one heck of a bad time.]]

* MysteriousStranger: A very unconventional example, in that he treats you like an old friend from practically the moment you meet and outwardly acts very friendly and laid-back. Because of this, it's not easy to notice just how little we find out about him as the story progresses or pick up on the subtle hints towards [[HiddenDepths just how much he's hiding from you]], but every once in a while, [[SurpriseCreepy you get an unexpected reminder]].

* NiceGuy: [[SurpriseCreepy Occasional creepy moments aside]], he's very friendly and always treats the player like an old buddy, even after they just met. [[spoiler:Makes sense after all, he's well aware that this most likely is not the first time he's met the player; him befriending them is his way to make a potentially genocidal player think twice about going through with it. He has his limits, however: kill his brother and he'll want nothing to do with the player, only appearing again to tell them off at the end of the game. Probably the only reason why he doesn't make them have a bad time then and there after killing Papyrus out of rage is because the player can still reset the timeline, thus undoing his battle/murder.]]

* LuckyTranslation: His name in the Japanese version is rendered as "Sanzu", which is coincidentally also the name of the [[https://en.wikipedia.org/wiki/Sanzu_River river in Japanese mythology]] which souls of the dead must cross before reaching the afterlife. The purpose of the river is to judge the sins you committed in life; the more sinful you were, the harder your path to the end will be. [[spoiler:The parallels to Sans' role as judge of your sins at the end of your playthrough are almost ''too'' on the nose.]]

* StealthPun: He's not fat, he's just big-boned.

* VagueAge: Sans is short, but has a deep voice. He has multiple jobs, but they are fairly simple. It's hard to tell whether he's a deep-voiced kid or a short adult. Most fans go with the latter.

* RoaringRampageOfRevenge: He ''unleashes hell on you'' for [[spoiler:all the innocent lives you've taken]], and if you went and [[spoiler:killed Papyrus]] as well, he's already let you know that you have exhausted his goodwill.

** Also, he avoids hard work, even if you kill all the leaders... but his love for his brother is stronger than his sloth. [[spoiler:If Papyrus becomes king, Sans will work really hard for him.]]

* PerpetualSmiler: Sans always has a mysterious smug, sneaky air about him, at least [[spoiler:when he's not exuding a TranquilFury attitude]] instead. Even when his eyes are giving away a different emotion, his giant grin never moves, most likely because he's a [[DemBones skeleton.]] The closest his grin ever changes is [[spoiler:when your blow finally connects,]] and even then it's just barely.

* ThresholdGuardian: He blocks your path in the Final Corridoor, and will judge you for all you have done across the game. If you pass with flying colors, he will basically say 'nice work'. If you've been engaging in VideoGameCrueltyPotential, especially if you kill Papyrus, he has some PlayerPunch to deliver. If you've been violent without going into outright KickTheDog territory, he basically leaves you to judge yourself unless you press the issue. [[spoiler:And if you've been going for the No Mercy route, he gets off his ass to stop you '' personally.'']]

* TrustPassword: If you reload a save after listening to his Judgment during a Pacifist run, he will give you a set of words, if you reset and talk to him again, will utterly fail to convince him that you're a time traveller. He will, however, give you a ''second'' password that, when reset and told to him again, causes him to give you a key to his room. The passwords are, respectively, [[TheGadfly "I'm a stupid doodoo butt" and "I'm the legendary fartmaster."]]

-->'''Sans:''' [[spoiler:sounds strange, but before all this i was secretly hoping we could be friends]].

* AttackDrones: Uses giant, floating, [[spoiler:demonic skulls called "Gaster Blasters" in his battle.]] [[spoiler:They fire [[WaveMotionGun wave motion beams]].]]

* BigBrotherMentor: If the PlayerCharacter goes strictly for the Pacifist Run, Sans will fill this role for the Human Child, occasionally giving some discreet assistance in the form of dropping hints, giving emotional support, and providing levity where he thinks its warranted.

* BossCorridor: The [[ExactlyWhatItSaysOnTheTin Last Corridor]] is completely empty until Sans suddenly appears and stops you in your tracks. Subverted in that he does not fight you, but he does assess your actions and deliver judgment, including some well-deserved {{Player Punch}}es if you screwed up. [[spoiler:Double subverted if you go on the No Mercy route, where he decides to actually step into the fray and gives you one hell of a fight.]]]]

* BreakoutCharacter: Easily one of Undertale's most iconic characters despite his role being smaller than more than half the main cast's on paper. [[spoiler: His boss fight, theme and lines in the Genocide Route led him to being so iconic]], that he ended up being the first Undertale character to make any sort of appearance in ''VideoGame/SuperSmashBros'', and even people on the internet who haven't played Undertale will likely recognize him.

** [[AlmightyJanitor Sans]] appears to be extremely knowledgeable about almost everything that goes on in the game but [[LazyBum spends all his time loafing around]] and [[PungeonMaster making puns]] for his own amusement. [[spoiler:It is heavily implied that Sans is some form of time traveler/scientist that has observed multiple timelines. The reason he's so lazy is that [[CosmicHorrorStory he knows the truth about how easily the world can be reset regardless of what he does]]. Only on the [[ApocalypseHow Genocide Route]], where the VillainProtagonist becomes a threat [[EvilOnlyHasToWinOnce not just to that timeline but all of them]], does [[NeutralNoLonger Sans actually become motivated enough to fight]], and he's by far the hardest boss in the game.]]
** Depending on the ending, Sans can get a job where he's surprisingly competent. If Mettaton becomes king, [[spoiler:Sans becomes his personal agent]]. If Papyrus is crowned king, [[spoiler:Sans does all the administrative work to spare him from broken by politics]].