History Undertale / TropesB

* BattleAmongstTheFlames: Most battles in the game take place against a featureless black backdrop. The battle with [[FinalBoss Asgore]] is notable for having an orange glow with sparks rising from the bottom of the screen, which is probably intended to [[InvokedTrope invoke]] this. [[JustifiedTrope Justified]] since Asgore fights using [[PlayingWithFire powerful fire magic]].

* BrokenAesop: Cleverly defied in the Playstation 4/Vita version with the Trophy system. ''Undertale'' is a game that constantly lampoons the 100Completion trope to no end, especially in [[spoiler:Flowey's speech in the Genocide route]], and has a general aesop on you having control over your own actions, but since Sony requires every game from [=PS4=] onwards to allow the players the ability [[AchievementSystem to earn trophies]], most of them are either story-mandated (simply reach the area in normal gameplay) or out of the way and add literally nothing (the Dog Shrine exclusive to the Playstation versions).

* BlobMonster: Moldsmal and its larger cousin Moldbygg are basically living Jell-O molds. They're described as [[AnythingThatMoves "curvaceously attractive"]] and loves some sexy wiggling, though the larger variant is more shy and prefers being left alone.

* BrainlessBeauty: [[{{Mooks}} Moldsmal’s]] battle description is [[ParodiedTrope a reference to this trope]]. [[note]][[LampshadeHanging Stereotypical:]] Curvaceously attractive, but no brains...[[/note]] Made even funnier since this monster [[AnythingThatMoves you can flirt with]] is a BlobMonster.

[[folder:Trope Bo-]]

* BewareTheSuperman: The Genocide Route runs with this as its main point, almost to the point of being a [[DeconstructedTrope Deconstruction]]. The twist comes in that it's [[spoiler:[[YouBastard you]], [[VideoGameCrueltyPotential the player]] who is the [[SaveScumming superpowered]] [[VillainProtagonist villain]].]] From an in-story standpoint, [[HumansAreCthulhu humans are overtly stronger than monsters]] and are limited only by [[KillingIntent their desire (or lack thereof) to kill]], [[ItGetsEasier which gets stronger as one's EXP (i.e. Execution Points) go up]]. [[MoodWhiplash The entire tone of the game changes]] from a [[WhiteAndGreyMorality morally ambiguous narrative]] where [[PoorCommunicationKills both sides misunderstand one another]], to one where [[OmnicidalManiac you are overtly and incontestably the evil party]]. Thematically, the entire point of this path is to deconstruct [[LevelGrinding the video game concept of grinding]] by [[spoiler:[[PlayerPunch making you realise just how cruel and psychopathic you'd have to be]] in [[SurprisinglyRealisticOutcome reality]] to go around [[AxCrazy senselessly killing creatures]] to get stronger]]. It's also exacerbated by the fact the player character's ability to save and reload [[GameplayAndStoryIntegration is an explicit in-universe power]], meaning that it's perfectly possible to undo missed opportunities to kill or even [[{{Sadist}} go back in time and kill a monster they've already killed again]]; the FinalBoss of the route [[LampshadeHanging lampshades]] this if you do it.

** The king of them all, crossing over with IronWoobie, is the goat monster [[spoiler:[[HundredPercentAdorationRating Asgore]]]]. Throughout the story, the player gets information that he may be a big softie. He is indeed very sweet and soft, yet sees [[WouldHurtAChild killing the protagonist]] as something he has to do, no matter how much he might not wish to.

* BadassBaritone:
** [[RoyalsWhoActuallyDoSomething Asgore Dreemurr]], the trident-swinging king of the monsters who [[ActionPolitician led his armies into battle himself]].
** [[spoiler:CrouchingMoronHiddenBadass Sans also has a pretty deep VoiceGrunting, second only to Asgore's.]]

* ButHeSoundsHandsome: If you type [[Music/TobyFox "Toby"]] in the essay question during the [[spoiler:Mettaton EX]] battle, he responds "Toby? What the hell is that? Sounds... sexy."

** [[ActionGirl Undyne]] was a very hot-headed kid, and once tried to fight Asgore to prove her strength. [[ActionPolitician Asgore]] merely kept [[NonchalantDodge dodging every one of her attacks]] and refused to fight the whole time. Afterwards, he offered to train her, which led to Undyne eventually [[AsskickingEqualsAuthority becoming head of the Royal Guard]].

* BonusBoss:
** In the Switch version, the Dog Shrine added in the [=PlayStation=] versions is replaced with one. [[spoiler:Near the end of the game, you can unlock a hidden red and blue door behind the Dog Shrine with the analog sticks. This leads to a hidden room containing Mad Mew Mew, a life-size statue of the titular protagonist of the "Mew Mew Kissy Cutie" series possessed by Mad Dummy.]]
** If you walk around the room in front of the Mysterious Door in Snowdin for two minutes straight, you'll encounter Glyde. As it's a tiny area that you'll quickly realize has nothing for you to interact with but some mushrooms that make a squeak sound when you click on them, you're incredibly unlikely to ever encounter them by accident. Unlike regular monsters and bosses, encountering and killing them isn't necessary for a No Mercy run.
** Even harder to find is So Sorry. To find them, you need to access a hidden area in Hotland on October 10, 8pm, that the game gives no indication even exists. On that day and time only, you will initiate an encounter with them by interacting with the art club sign in the hidden room. Like Glyde, they are a boss fight that isn't necessary to trigger and defeat in order to proceed with a No Mercy run, and in fact can't be found during those runs — the area to access the hidden room is sealed off by Alphys. Glitching your way there anyway reveals an empty room [[DevelopersForesight with a sign that says "Art club is cancelled!"]]

** Glamburgers from MTT Resort seem to be a huge hit despite being made of sequins and glue.[[note]][[AluminumChristmasTrees Edible sequins do exist]], but judging by [[EveryoneCallsHimBarkeep Burgerpants’]] reaction, this doesn’t seem to be what the burgers are made of.[[/note]]

* BadFuture: Pretty much every ending that's not the GoldenEnding is either implied or outright stated to be one of these. In all endings, the human souls vanish, taking any hope the monsters had of escaping with them. On top of this, the Underground can become completely militarized, an {{Egopolis}}, or the monsters can be left on the brink of extinction (if not [[KillEmAll outright driven extinct]]). Even in the best non-GoldenEnding circumstance where [[EverybodyLives you spared everyone]][[note]]with the only casualties being [[spoiler:Asgore and maybe Flowey at the very end; the former ''only'' survives in the GoldenEnding (as he will otherwise be killed by Flowey or kill himself if you spare him), and the latter being spared or killed only changes TheStinger, not the main part of the Neutral Ending itself]][[/note]], while the monsters' situation isn't all that bad, they still lost the human [=SOULs=] that [[spoiler:Asgore]] has gathered, and [[spoiler:while Alphys is researching alternative ways to break the barrier at Toriel's behest, [[AmbiguousSituation it's left ambiguous as to whether or not she has any chance of succeeding]]]]. At any rate, it doesn't look good for the monsters.

** If you lose to [[LargeHam Papyrus]], he will capture and imprison you… in an unlocked shed next to his house, with bars large enough for you to walk through the only thing blockig the way out.

** The very last chords of "Bring it In, Guys", the theme for the ending credits, are the very first chords from "Once Upon a Time", the first song you hear upon starting the game. [[spoiler:Subverted when it gets interrupted and you get more credits with a different song]], and then [[spoiler:DoubleSubverted when the ending of that song is another reprise of Once Upon a Time on the piano.]]

* BrainsAndBrawn: Alphys is short, chubby, and and GadgeteerGenius who never fights the player and evacuates the monsters on the Genocide Route. Undyne is tall, muscular, and a [[HotBlooded very confrontational]] ActionGirl who will confront the PlayerCharacter directly on all routes of the game. [[DownplayedTrope However]], Undyne is still fairly smart and [[AbsentMindedProfessor Alphys is rather scatterbrained]].

** [[spoiler:Mettaton]] was a non-coporeal ghost who very badly wanted to have a physical form, but despaired that it would never happen because his ideal body was so unusual for a monster — [[PinocchioSyndrome he wanted to look like a human]]. His friend Alphys made him a NighInvulnerable robotic physical body to inhabit in the meantime while she worked on creating one that better fit what he wanted. The new body, called his EX form, is exactly what he wanted but consumes a lot of power, and [[spoiler:Mettaton]] can't remain in that form for long. The epilogue of the GoldenEnding shows him happily alternating between the two forms at will.

** The Annoying Dog is the AuthorAvatar of Creator/TobyFox, complete with AuthorPowers, but all he does is play pranks of people and never interferes with the events no matter what you do. [[spoiler:The only exception is that one ending where you kill all the bosses but none of the encounters, and he ends up king.]] And even then, according to Sans, all he does is laying around.
** [[spoiler:All Sans does during the game is watch you from various distances, prank you, deliver jokes, and make the [[BreadEggsMilkSquick occasional death threat]]. He's perfectly capable of carying out those death threats.]]

** Asgore has a purple one, and on the overworld it seems to be the reason for how much space he takes up compared to everyone else… then he throws it back during his boss fight and it's revealed that he's just that huge.

* BadFuture: Pretty much every ending that's not the GoldenEnding is either implied or outright stated to be one of these. In all endings, the human souls vanish, taking any hope the monsters had of escaping with them. On top of this, the Underground can become completely militarized, an {{Egopolis}}, or the monsters can be left on the brink of extiction. At any rate, it doesn't look good for the monsters.

** [[spoiler:Just like his brother, [[FinalBoss Sans]] has attacks based off [[BadWithTheBone bones]], plus InterfaceScrew powers ([[TheFourthWallWillNotProtectYou something often associated with horror]]), and terrifying-looking [[EnergyWeapon laser skull dragons]].]] However, despite the… intensity of his magic, he's still a fundamentally good guy, and if you ever see him use that magic, then you probably deserve what's coming for you.

* BaitAndSwitchBoss: At the end of the [[GoldenEnding True Pacifist Route]], it seems like you’re about to confront [[spoiler:[[FinalBoss Asgore]]]] once again… and then [[spoiler:[[MyBelovedSmother Toriel]] swoops in and [[BigDamnHeroes saves you]]]]. [[spoiler:Afterwards is a heartwarming cutscene of you reuniting with your friends, and then another where [[BigBad Flowey]] steals the [[PoweredByAForsakenChild human souls]] and the souls of your friends to become the OneWingedAngel [[TrueFinalBoss Asriel Dreemurr]].]]

--->'''Muffet:''' [Alphys] even left a route for me to escape from~ She said she would block off the rest of Hotland for me~ Foolish nerd~ A spider NEVER leaves her web~ (Except to sell pastries~) Ah, but I do feel a little regret over it now...yes, I should have wrapped her up when I had the chance~ She looked like she would have made a juicy donut~~

** We’ve just heard about [[MurderousMalfunctioningMachine Mettaton going nuts]], and then [[IncomingHam he bursts into the room]]. For a while, he seems [[LargeHam really fun and entertaining]]… and then he tries to kill you. [[DownplayedTrope Downplayed]], because he’s still very entertaining after this, and eventually [[spoiler:subverted when he reveals he never was trying to kill you, but then [[DoubleSubvertedTrope double subverted]] when he actually ''does'']].

** [[spoiler:Flowey pulls one on ''you'', the player, if you get the neutral ending and spare him. In order to get everyone in the underground into one place and absorb their [=SOULs=], he goads you into going down the Pacifist route, because he knows that you want to "win" and get the "best ending." Do what Flowey predicted, and he can take the [=SOULs=] of every single monster in the underground, which is just barely enough power to equal the seventh human [=SOUL=] he needs to complete his transformation into Asriel Dreemurr.]]

** [[ShrinkingViolet Alphys]] is carrying a lot of baggage and self hatred after [[spoiler:[[GoneHorriblyWrong the creation of the Amalgamates]]. Several families who think she’s holding their relatives hostage for no reason are angry at her, and judging by a phone call from Undyne, Alphys was nearly DrivenToSuicide before she met her friend]]. Alphys’ arc in the True Pacifist Route involves her learning to love herself, and eventually she decides to tell the truth [[spoiler:about the [[BodyHorror Amalgamates]]]].

** [[ShrinkingViolet Alphys]] [[spoiler:conducted experiments using [[AppliedPhlebotinum determination]], a fantastical human power, in an attempt to break the barrier between the underground and the human world. This resulted in the creation of the [[BodyHorror Amalgamates]], horrific (though [[CreepyCute surprisingly friendly]]) chimeras that are [[AndIMustScream under great suffering]], the [[GoneHorriblyWrong creation]] of [[BigBad Flowey]], and possibly the fate of [[DummiedOut W.D. Gaster]]. No wonder [[AmbiguousDisorder Alphys is so screwed up]] after all of this]].

** The PlayerCharacter, who can [[GoldenEnding free the monsters]] [[ActualPacifist without hurting a fly]], or [[KillEmAll destroy the world]] despite being a [[TheOphelia cute]] [[CreepyChild little]] [[EnfantTerrible kid]].

* BadassFamily: The [[RoyalsWhoActuallyDoSomething Dreemurrs]]. Toriel has 80 ATK and DEF and is a [[AddedAlliterativeAppeal powerful]] [[PlayingWithFire pyromancer]]. Asgore has the same abilities, but with combat training and a trident, [[ActionPolitician led his own armies into battle]] in the [[GreatOffscreenWar War of Humans and Monsters]], ''and is capable of an InterfaceScrew.'' The only other characters capable of this are the three [[FinalBoss final bosses]]! Also, two of those bosses are alternate forms of [[spoiler:Asriel, Asgore and Toriel’s son]]. And of course, Chara/[[spoiler:[[CanonName Frisk]]]] can [[BadassPacifist save the monsters without hurting a fly]] or [[KillEmAll destroy]] [[ApocalypseHow the world]] '''[[AsLethalAsItNeedsToBe with a stick]]'''.

** [[PungeonMaster Sans]] is introduced as a terrifying presence stalking you through the woods… [[BaitAndSwitch up until he lets loose]] [[MoodWhiplash with a ridiculous "whoopee cushion in the hand" gag]]. From that point on, he presents himself as a [[LazyBum lazy]], laid-back comic relief character who'd rather hang out with you at the local restaurant than actually do his job. As he eventually confesses, he even promised [[MyBelovedSmother Toriel]] he'd watch over and protect you… and if it hadn't been for that promise, [[spoiler:[[MoodWhiplash he would have killed you when he first laid eyes on you]]. It's implied [[HiddenDepths he knows far more about the situation than he lets on]], and even [[BigBad Flowey]], in certain lines, admits [[HorrifyingTheHorror he's terrified of Sans]], and considers him [[FinalBoss the most dangerous monster in the Underground]]. [[KillEmAll If you kill absolutely everyone you run across]], you find out why. ''Painfully''. [[NeutralNoLonger Sans will decide that he can't ignore such a threat]], and fight you himself. He is, by a wide margin, [[ThatOneBoss the most difficult challenge in the game]]]].

** PlayedForLaughs if you're fighting Undyne on a non-[[KillEmAll Genocide Route]]; [[MemeticBadass she'll suplex a boulder just because she can, then suplexes ten boulders for the same reason, then finally suplexes ''herself'' "just to prove nothing is impossible"]]. She also manages to [[spoiler:produce her own [[{{Determinator}} determination]], which monsters are stated to be unable to do. She adamantly refuses to die when the player kills her — until she melts. In the [[EarnYourBadEnding Genocide Route]], the player character has to kill her twice because she reforms herself into [[OneWingedAngel a more powerful form]] just to stop you]].

* BigBadSlippage: The PlayerCharacter can do this depending on the player’s actions, going from an [[ChildrenAreInnocent innocent]] MessianicArchetype on the [[GoldenEnding True Pacifist Route]] to [[VillainProtagonist the]] [[OmnicidalManiac Fallen]] [[EnfantTerrible Child]] on the [[KillEmAll Genocide Route]].

* BloodbathVillainOrigin: A [[KillEmAll Genocide Route]] starts out like this, with the player being required to track down every RandomEncounter in the NoobCave and kill them.

** The [[MeaningfulName Last Corridor]] (so named by the SavePoint there) is a stately hallway bathed in gorgeous yellow light which obviously leads the player straight to the final encounter with the king. However, one dialogue occurs in the middle of this corridor, and it includes a major [[TheReveal reveal]]. [[spoiler:On a [[KillEmAll Genocide Route]], the FinalBoss[[note]]as the next two targets, Asgore and Flowey, [[PostFinalBoss suffer death by cutscene]][[/note]] [[MarathonBoss Sans]] is fought ''[[BossRoom in the corridor itself]]''.]]

* BossDissonance: For the most part, the [[KillEmAll Genocide Route]] is very easy. There’s a certain point where the player’s [[ItGetsEasier LOVE]] is high enough to OneHitKill most enemies, which ironically means the only place on the Genocide Route where common {{Mooks}} pose a challenge is the early [[NoobCave Ruins]] when you haven’t built up a lot of EXP. However, the route’s two bosses, [[spoiler:Undyne the Undying and Sans]], are extraordinarily difficult and unforgiving, far more so than even the TrueFinalBoss of the Pacifist Run.

* BrainsAndBrawn: Alphys is short, chubby, and and GadgeteerGenius who never fights the player and evacuates the monsters on the [[KillEmAll Genocide Route]]. Undyne is tall, muscular, and a [[HotBlooded very confrontational]] ActionGirl who will confront the PlayerCharacter directly on all routes of the game. [[DownplayedTrope However]], Undyne is still fairly smart and [[AbsentMindedProfessor Alphys is rather scatterbrained]].

** [[BigBad Flowey]] the [[FoulFlower Flower]] [[spoiler:is really a reincarnation of [[AwesomeMcCoolname Asriel Dreemurr]], the dead prince of the monsters. [[ThanatosGambit When Chara sacrificed themself so Asriel could use their soul]], he went up to the human village where Chara first came from. However, they saw a monster holding a dead body and assumed the worst, and because [[SuicidalPacifism Asriel refused to fight]], the humans mortally wounded him and he died in his father’s garden. However, many years later, Alphys injected a flower with Asriel’s dust on it with [[AppliedPhlebotinum determination]] as part of her experiments, bringing him back to life as Flowey. This also resulted in his gaining SaveScumming powers due to the sheer amount of determination inside of him not allowing him to die. However, without a soul, he was cursed with LackOfEmpathy, and so, he [[CosmicHorrorStory trapped the world]] in a GroundhogDayLoop, [[HundredPercentCompletion endlessly exhausting all possible events]] as [[SanitySlippage his mental state slowly deteriorated]] into the PsychopathicManchild he is now]].

** The final boss of the [[KillEmAll Genocide Route]] has a relatively lengthy introductory monologue saying how you should be burning in hell for all you've done. [[spoiler:If you go for a rematch after getting past his opening barrage for the first time, there's a good chance [[NoFairCheating he will skip his monologue at random straight into his opening barrage to catch you off-guard]].]]

* BestFriend: The monster prince Asriel Dreemurr and [[HelloInsertNameHere Chara]], the first human to fall into the Underground after the Barrier was erected, have been best friends in the BackStory, but their friendship ended very, very badly due to circumstances they had no control over: Chara fell ill and died, but not before asking Asriel to take them to see the surface one last time. Asriel complied, but [[PoorCommunicationKills the terrified villagers assumed that he killed Chara and lynched him for it]]. [[AlmostDeadGuy Asriel crawled back into the underground before dying]] and turning to dust in the royal garden. [[spoiler:Much later, a flower from said garden was injected with human determination by Alphys, creating [[FoulFlower Flowey]], the BigBad of the game, while Chara [[AmbiguousSituation somehow]] continued their existence as a malicious spirit who [[DealWithTheDevil lends its power to]] [[CanonName Frisk]] in the [[KillEmAll Genocide Route]].]]

* BetrayalByOffspring: [[spoiler:The king and queen had two children, Asriel and [[HelloInsertNameHere Chara]]. [[UsedToBeASweetKid Asriel]] eventually becomes [[BigBad Flowey]], who traps the world in a GroundhogDayLoop, [[HundredPercentCompletion killing every monster in the underground multiple times and hurting them emotionally in every possible way]], [[AntagonisticOffspring including his parents]]. During the events of the game, Flowey can also be seen [[{{Patricide}} directly killing Asgore]] and destroying his soul, as well as absorbing said soul in a different timeline for power. As for Chara, [[AmbiguousSituation we don’t know much for certain]], but we do know [[AmbiguouslyEvil they’re connected in some way to the events of the]] [[KillEmAll Genocide Route]].]]

* BewareTheSuperman: The [[KillEmAll Genocide Route]] runs with this as its main point, almost to the point of being a [[DeconstructedTrope Deconstruction]]. The twist comes in that it's [[spoiler:[[YouBastard you]], [[VideoGameCrueltyPotential the player]] who is the [[SaveScumming superpowered]] [[VillainProtagonist villain]].]] From an in-story standpoint, [[HumansAreCthulhu humans are overtly stronger than monsters]] and are limited only by [[KillingIntent their desire (or lack thereof) to kill]], [[ItGetsEasier which gets stronger as one's EXP (i.e. Execution Points) go up]]. [[MoodWhiplash The entire tone of the game changes]] from a [[WhiteAndGreyMorality morally ambiguous narrative]] where [[PoorCommunicationKills both sides misunderstand one another]], to one where [[OmnicidalManiac you are overtly and incontestably the evil party]]. Thematically, the entire point of this path is to deconstruct [[LevelGrinding the video game concept of grinding]] by [[spoiler:[[PlayerPunch making you realise just how cruel and psychopathic you'd have to be]] in [[SurprisinglyRealisticOutcome reality]] to go around [[AxCrazy senselessly killing creatures]] to get stronger]]. It's also exacerbated by the fact the player character's ability to save and reload [[GameplayAndStoryIntegration is an explicit in-universe power]], meaning that it's perfectly possible to undo missed opportunities to kill or even [[{{Sadist}} go back in time and kill a monster they've already killed again]]; the FinalBoss of the route [[LampshadeHanging lampshades]] this if you do it.

** [[VagueAge Though their ages are left unstated]], Sans is canonically older than Papyrus. Sans openly admits that his [[SociallyAwkwardHero dorky]] [[WideEyedIdealist and painfully]] [[NiceGuy nice]] ManChild brother is the single coolest person he knows, and he is very protective of Papyrus and his happiness. The only thing that actually gets on his bad side is [[RelativeButton killing Papyrus]] in a playthrough, which turns him from a wacky side character into someone who [[HeroicBSoD disappears from the rest of the game]] and only appears again in the epilogue, where he judges your actions and leaves you with what amounts to "[[YouBastard go to hell]]". [[spoiler:The only reason he doesn't give you [[ThatOneBoss a bad time]] is because of his promise to Toriel. Plus, [[HeKnowsAboutTimedHits he's aware you can start another playthrough and thus undo his murder]], though naturally he'll still think you're a bastard.]] Speaking of a bad time, [[spoiler:if the game detects that you're on a [[KillEmAll Genocide Route]], Sans will warn you prior to the fight with Papyrus to stop killing or [[IWarnedYou you're really not going to like what happens next]]]]. If you ignore his warning and make it to the end of said route, he shows up again and, [[NeutralNoLonger deciding he can't afford to not care anymore]], [[spoiler:[[SNKBoss and proceeds to utterly pulverize the living daylights out of you]]]]. He never references his brother directly while doing this, but examining his dialogue makes it pretty clear that he's on the forefront of his mind — [[spoiler:the very first thing he asks you is whether or not you think it's possible for anybody, no matter how evil they are, to be a good person if they just try hard enough, and then laughs before you can give an answer, an IronicEcho of Papyrus's last words when you murdered him. And if you finally manage to persevere through the battle and kill him, his own last words are [[TearJerker telling Papyrus he's going out to eat and asking if he wants him to get him anything]], meaning he's either hallucinating or can see his brother waiting for him in the afterlife]].

** [[SmallNameBigEgo Papyrus]] is a LargeHam who also [[{{Narcissist}} thinks he’s the greatest monster to ever live]]. [[ThirdPersonPerson He calls himself "the great Papyrus"]], and is always boasting about how great he is and how he will one day achieve everything he wants. However, he is far from malicious; indeed, [[NiceGuy he's one of the nicest]] [[AllLovingHero characters in the entire setting]]. He doesn't just have high confidence in himself: he has high confidence in everyone. He always has great things to say about you during your trip through Snowdin and even tries to cheer you up when he thinks you're being too harsh on yourself (even if you were actually trying to insult him). Even when the player is [[OmnicidalManiac the darkest they can be]] on a [[KillEmAll Genocide Route]], [[WideEyedIdealist Papyrus]] still thinks they can be good if they really try. Papyrus is also easy to befriend, and losing to him in his battle just leads to your capture in a CardboardPrison, because he wants the protagonist alive. [[HiddenDepths He's also shown some traits that can be surprising]] if you just see him as an egotistical ManChild. He can be pretty sly and manipulative when he wants to, such as when he convinces Undyne to try befriending the protagonist by [[BatmanGambit presenting it as a challenge]]. He's also more aware of what's happening around him than it seems; when he becomes king in one of the Neutral endings, he initially says that while he believes Sans' lies about his friends going on an "extended vacation", it's subtly hinted that he knows that they're probably gone for good.

** Conversely, on the [[KillEmAll Genocide Route]], as well as the other routes [[DownplayedTrope to a degree]], [[spoiler:we have [[FriendlySkeletons Sans the skeleton]], who [[AlmightyJanitor presents himself as the weakest monster in the Underground]], but guides you throughout your journey and tries to convince you not to murder the monsters. However, you can choose to become a VillainProtagonist who [[AxCrazy murders]] [[OmnicidalManiac every]] [[EnfantTerrible monster on sight]] [[LevelGrinding for the sake of power]]. [[VideoGameCrueltyPotential If you decided to commit genocide]], [[FinalBoss Sans will fight against you]].]]

** [[BeautifulVoid New Home]] is a much larger area, with no fights before [[BigBad Asgore Dreemurr]]. There are, however, a number of "fights" where the monsters do not attack; the "fights" are solely there to provide [[ExpositionDump exposition]]. This trope is played differently in a [[GoldenEnding True Pacifist Route]]; [[spoiler:there, you only fight one boss ([[TrueFinalBoss Asriel Dreemurr]]) but briefly encounter Asgore before [[BigDamnHeroes Toriel attacks him]], followed by all other monsters, including bosses, briefly appearing. Meanwhile, in a [[KillEmAll Genocide Route]], there are technically two bosses ([[MarathonBoss Sans]] and [[OneHitKill Asgore]]), but the latter is defeated in a cutscene with no player effort]].

* BottledHeroicResolve: Determination is this for monsters that have the willpower to handle it. However, the monster will eventually melt, meaning determination is a last resort for them. [[spoiler:We see this on the [[KillEmAll Genocide Route]] when [[ActionGirl Undyne]] becomes [[SuperMode Undyne the Undying]].]]

* BrightIsNotGood: The main villains of the game are this. [[FoulFlower Flowey]] has bright yellow petals, and [[spoiler:his [[BotanicalAbomination Photoshop]] form isn’t a slouch on bright colors either]]. The other villain, [[spoiler:the [[OmnicidalManiac Fallen]] [[EnfantTerrible Child]], wears a bright green and yellow shirt at the end of the [[KillEmAll Genocide Route]] as they discuss slaughtering everyone for power]].

* BallisticBone: During the boss fight against [[DemBones Papyrus]], his attacks consist of throwing [[BadWithTheBone bones]] of all kinds at you. If you check out his house later you'll even see a box full of them. Makes sense considering he's an ambulatory skeleton. [[spoiler:Sans]] also uses similar attacks, but ramped UpToEleven in terms of speed, frequency, patterns, e.t.c.

** The Dreemurrs seem to like snails enough that Toriel has an entire bucket of them in her room, and cooks snail pie. [[UpToEleven It’s also implied that Napstablook can support himself and his snail farm on money from Asgore alone, and only coming once a month at that]]. [[AdiposeRex No wonder Asgore is so big...]]

** [[BigBad Flowey]] is a {{Sadist}} who loves seeing you squirm before he kills you. [[spoiler:In the case of [[FinalBoss Photoshop Flowey]], he literally ''[[UpToEleven never kills you]]'' because he's having too much fun locking you in a GroundhogDayLoop of painful death.]]

** [[spoiler:After [[BigBad Flowey]] takes the human souls and becomes [[EldritchAbomination Photoshop Flowey]], ''[[UpToEleven nothing]]'' exists except Flowey and the player, as Flowey destroyed it all.]]

* BosssUnfavoriteEmployee: In addition to being a major celebrity, Mettaton also manages a resort. He's generally a BenevolentBoss to the resort's employees… except for [[BurgerFool Burgerpants]]. He made ''[[UpToEleven an entire album]]'' purely dedicated to telling Burgerpants how bad at his job he is.

* BottomOfTheBarrelJoke: Sans pranks the human with a whoopee cushion twice. However, these still work surprisingly well with the individual scenes, given Sans’ immature sense of humor. Taken UpToEleven with Sans’ “[[BigStupidDoodooHead passwords]]” to confirm you’re a time traveler.

** [[spoiler:Flowey pulls one on ''you'', the player, if you get the neutral ending and spare him. In order to get everyone in the underground into one place and absorb their [=SOULs=], he goads you into going down the Pacifist route, because he knows that you want to "win" and get the "best ending." Do what Flowey predicted, and you'll face Asriel.]]

* BotanicalAbomination: At the end of the Neutral route, [[spoiler:Flowey the Flower]] gains the power of the human souls and [[OneWingedAngel becomes an enormous, omnipotent]] beast called [[spoiler:Omega Flowey or Photoshop Flowey]]. This form combines plant-like features with [[MechanicalAbomination machine parts]].