History YMMV / Undertale

** Overlaps with DoNotDoThisCoolThing. Many fans of the game actually enjoy the No Mercy route, despite it having a goal of making players feel terrible and unsatisfied. These tend to be [[TrueArtIsAngsty story-focused fans]] (the dark, tragic plot can be just as gripping as the normal story, and [[TheApocalypseBringsOutTheBestInPeople it shows many characters at their best]]) and {{Challenge Gamer}}s ([[spoiler:with the route hosting two extremely tough fights that require players to seriously master the game mechanics in order to succeed]]). It's worth noting that [[spoiler:the majority of Sans's popularity]] comes from the No Mercy route. What tends to make people play it deliberately is that the LevelGrinding condition is otherwise so tedious that most people would become aware of it from hearsay, tempting them to try it out.

* TrueArtIsAngsty:
** Played straight with Sans. [[spoiler:His mysterious DarkAndTroubledPast and his ever-famous boss battle at the end of the Genocide Route is a huge FanficFuel amongst fans for showing his StoicWoobie side.]]
** Some of the fans are still playing this trope straight with [[spoiler:The Fallen Child]] by giving them [[spoiler:extremely tragic backstories, portraying them as self-harming and suicidal or even making all their presumable existence in Frisk's head look like a form of AndIMustScream, despite of their rather sassy and enthusiastic attitude in-game[[labelnote:note]]If you belive they're NarratorAllAlong.[[/labelnote]].]]

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** Snowdrake speaks with heavy ''[[KansaiRegionalAccent Kansai-ben]]'' in the Japanese translation, due to the Kansai dialect's association with comedy acts.

** As mentioned under DracoInLeatherPants, [[spoiler:the Fallen Child]] ''[[RiddleForTheAges may or may not be]]'' this. Their backstory is vague, and it's unknown whether [[spoiler:they really wanted to free all monsters or destroy humanity]], and to complicate matters further, there's a widely-growing chunk of the fanbase who believe [[spoiler:the Fallen Child is really [[NarratorAllAlong the narrator]], and that they only become corrupt in the Genocide route]]. If that really is the case, then all of the AxeCrazy OmnicidalManiac depictions of [[spoiler:the Fallen Child]] fall under this.

** Sans quickly became the game's most popular character as a result of [[spoiler:his HiddenDepths in the Genocide Route as someone whose mostly-ambiguous DarkAndTroubledPast results in him being [[SadClown deeply apathetic behind his goofy exterior]], and for being an insanely strong {{Superboss}} who breaks the rules of the game in creative ways]]. He became a popular subject for fanworks, especially alternate universe fics that [[spoiler:emphasized his depression]]. However, his popularity grew so rapidly that it led to a widespread backlash both in and out of the ''Undertale'' fandom, causing his and the game's presence in pop culture to collapse in on itself in 2017. By the time he became a Mii Fighter costume in ''VideoGame/SuperSmashBrosUltimate'' two years later, Sans became better-known as a subject for ironic memes that played off his past overexposure, with his fandom being seen as a cautionary tale about what happens when an EnsembleDarkhorse gets too popular too quickly. In fact, a good portion of jokes about [[spoiler:fellow {{Superboss}} Spamton]] in ''VideoGame/{{Deltarune}}'', who garnered a similar reputation, revolve around being next in line to effectively be the next Sans.

** Papyrus thinks he is ''the'' most awesome person in the whole world. It's hard not to love him because he's always unflinchingly nice and helpful to everyone. He never looks down on people with smug superiority, but wants to help everyone else be ''almost'' as awesome as he is! (Equaling him is impossible.)

** If you call Papyrus at the snail farm he will mention that the snails are "just like his brother;" as they're "round, slow, and... always emitting slime?" He's most likely referring to the ketchup Sans drinks leaking out of his ribcage (or just being a {{Cloudcuckoolander}}), but [[ADateWithRosiePalms you really never know.]] It doesn't help that if you call him again he adds "Emitting slime... that's just what brothers do!", as if you just questioned him about it.

** Like explained below, [[spoiler:the Endogeny fight ends with]] the goofy "Dogsong" playing. While it would normally sound ridiculous, [[spoiler:it sounds like a relief here, because [[https://www.youtube.com/watch?v=2Pf_liZf5I8 this song was playing before]], and also because it shows that deep down, it's a BigFriendlyDog who was more curious than aggressive and needed affection before anything else]].
** Wingdings is one of those [[InherentlyFunnyWords inherently funny words]], and it's a pretty silly font. That doesn't make Dr. W.D. Gaster or the line ''"Beware the man who speaks in hands"'' any less chilling.

** A possibly deliberate example. The battle against the [[spoiler:Endogeny Amalgamation. It's a big, faceless dog abomination... that's still just a playful dog in the end]]. The fact that the hilarious "Dogsong" starts playing when it's happy enough just seals the deal.

* TheScrappy: So Sorry, who is one of the game's {{Bonus Boss}}es. Like Muffet, he was included as a backer's Kickstarter reward, but he has received significant hate for quite a few reasons[[note]]The backer in question not only paid ''$1000'' for his character to be in the game, but most fans view the character to be pandering to the UsefulNotes/FurryFandom a bit too much, especially considering that the character has been used in fetish art outside the game. Others also consider it to be a shameless self-insert of the backer's fursona, done in the interests of self-promotion, rather than trying to add something creative and original[[/note]]. Nearly any [=YouTube=] video of the fight with him is an explosion of disdain that leads to flame wars, and has noticeably more dislikes than other ''Undertale'' videos. Even players that don't care about his character find him to be a GoddamnedBoss with frustrating attack patterns and difficulty in being spared/killed. The vitriol has even spread to the point where the backer has been harassed, requiring [[https://twitter.com/tobyfox/status/645736554317639681 Toby himself to make a tweet asking them to stop]].

** To a lesser extent, [[spoiler:Memoryhead in the True Lab. They're the only Amalgamate that doesn't obviously resemble ''any'' of the monsters you've previously encountered, unlike the others, and they seem to act like some sort of living glitch (their speech is garbled and blocky, the battle text itself is random, and most of the [=ACTs=] are from your non-battle menu). Since their appearance resembles a cross between skulls and [[VideoGame/{{EarthBound}} Giygas]], this has led to people [[WildMassGuessing wondering]] if Memoryhead is related to W. D. Gaster in some fashion.]]

** A few, but two that stand out are [[spoiler:Frisk and/or Chara]] with [[VideoGame/YumeNikki Madotsuki]] due to all of them being children in ''VideoGame/EarthBound''-esque games with an affinity for knives, [[spoiler:and in Frisk's case, sharing identical facial expressions throughout the entirety of their respective game]].
** Asgore/[[VideoGame/SuperMarioBros Bowser]] is also a [[HoYay popular one]], due to the fact that while they're both [[PlayingWithFire fire-powered]], [[BenevolentBoss well-regarded]] kings [[spoiler:and fathers]], and they're also borderline {{Foil}}s to each other — Bowser is a greedy {{jerkass}}, while Asgore is a kind HeartbrokenBadass.

** These days, the ''VideoGame/{{EarthBound}}'' fandom ironically has issues with the ''Undertale'' fandom. People got tired of people bringing ''Undertale'' up in all ''MOTHER''/''[=EarthBound=]'' discussions (''[[DiscreditedMeme especially]]'' "[[WebVideo/GameTheory Sans is Ness]]" wisecracks), and some places ban all mentions of the game entirely.
** Many less mature ''Webcomic/{{Homestuck}}'' fans are rather aggressive in their dislike of ''Undertale'' and its fandom, mostly thanks to ire over MEGALOVANIA's usage and subsequent explosion in popularity causing many to assume it came from the game, when it was in fact featured within ''Homestuck'' several years prior. [[note]]While the song first debuted in an ''VideoGame/{{EarthBound}}'' [[VideoGame/TheHalloweenHack hack]] made by Toby, Homestuck ''was'' the first truly popular work with an actual fanbase to feature the song before ''Undertale''.[[/note]] This is notably mostly rather one-sided, with the majority of ''Undertale'' fans bemoaned by these people likely having little clue on ''Homestuck's'' existence for the most part.

** For the same reasons as the ''OFF'' fandom, ''VideoGame/{{EarthBound}}'' and ''[[VideoGame/{{MOTHER3}} MOTHER 3]]''. It helps that Toby Fox had previously contributed to the community. There's a lot of crossovers in their ranks, usually under the name "[=MOTHERtale=]".

** Muffet is cute either way, but in-game she has some clearly non-human features: besides the obvious, she has a long thin neck, [[TheNoseless no nose]], and stick limbs. A good deal of fan artists ignore this and draw her as a purple-skinned, but otherwise normal-looking girl with fangs, three extra eyes, and six arms[[note]]Most of these focus more on her out-battle sprite, who looks less deformed than her in-battle one[[/note]].

** Asgore. While still having many fanwork focusing on his [[AuthorityEqualsAsskicking badass]] and [[BigBeautifulMan attractive]] traits, many fans love to crack jokes about him [[spoiler:being cucked by a skeleton, constantly rejected by his ex-wife, killed by a child or a flower]] or his status as a GiverOfLameNames.

** Fittingly, Hotland/Core is this on a Genocide run as well due to the number of kills (40) being more than the three previous areas ''combined''.

* MoralEventHorizon: [[spoiler: Killing Flowey and giving your SOUL to Chara in order to play the game again is the point where, short of messing with the game’s configuration files, it becomes impossible to abort a Genocide Route and doing so permanently taints the [[GoldenEnding True Pacifist ending]]. Even after killing every enemy in Hotlands (which locks you into the Genocide Route ending) it is still possible to abort by resetting the SAVE file.]]

** As mentioned under HypeBacklash, the fact that the game has to be played blind for the full experience is a huge mark against it for a lot of people wary about the game for one reason or another, since most responses to "Why should I give this game a chance?" can be summed up in "You just have to take my word for it because everything I could praise about it is a spoiler."

** While ''Undertale'' is a great experience, the fandom talks it up too much sometimes for the unfamiliar, and they are also very prone to revealing spoilers (especially Tumblr). Some people would rather not play the game at all just to avoid the risk of disappointment.
* HypeBacklash: Not as fierce as others, but still inevitable with a game that received such a storm of popularity and critical acclaim.
** Putting aside people who hate it [[ItsPopularNowItSucks simply for being popular]], the most common criticism from players is that the story is good, but the bullet hell mechanics often turn people away. There's also many who don't agree with the way the message is handled in the No Mercy route, with the primary complaint being [[spoiler:the game permanently locking you out of the Golden Ending in all future playthroughs]] is overly harsh. Another portion of this is that every single reviewer for the game recommended playing it first, and many agree that the best way to play the game is almost entirely blind, or completely blind, which becomes a problem due to the advent of message boards and Youtube.
** While most fandoms tend to spread quotes, images and references to their fandom on things that have nothing to do with it, the ''Undertale'' fandom is currently one of the most persistent, causing quite a lot of backlash from people that are by now annoyed of all the "X is filling you with Determination" memes, comparing random characters (sometimes even of older series or games) to ''Undertale'' characters and similar.
** This is especially true for [[LetsPlay Let's Players and streamers]], some of whom think they should take a certain route, and others who feel they should play the game blind. It's made some of them refuse to LetsPlay the game at all. Those that ''do'' play the game seem to regret it later since no matter what they do, it's never good enough. Most start playing blind, but if they don't follow the Pacifist route on the first time or miss a small detail, then they're accused of "playing the game wrong". The most common case is when the Let's Player doesn't know how to spare Toriel, so they kill her, and the entire comment section is filled with angry comments demanding the player to start the game over and "do it right this time". If the LP'er ''does'' reset, they get further angry comments calling them a "sissy". Let's Players that have proclaimed to play all variants often get yelled at for playing "in the wrong order". While half the fandom thinks that one needs to play No Mercy and Neutral first to really enjoy the perfect ending, others call the player stupid because by doing that they would just not get to see the charm of the game and lose interest.

** For a good while, if you were to go on any social media page that wasn't STRICTLY related to Undertale and made a public comment referencing this game or even how something about the current page reminded you of it, your odds of getting yelled at to [[GetOut get out]] for bringing Undertale to that unrelated medium were quite high for many of the reasons listed above and below. This has however become significantly less common since at least 2018.

** Due to how surprisingly deep this game is and Music/TobyFox [[DeathOfTheAuthor not going into detail about what things in the game mean]], many folks have come up with other interpretations as to what the game means. Some feel that how [[spoiler:Chara steals your soul at the end of a No Mercy run and how the only way to fix it is to delete your save file]] gives off the moral, "The only way to move forward is to [[BurningTheShips burn your bridges]]."

** Speaking of Sans, you'd be forgiven for thinking that when his eye glows, it only glows blue, given how often it's depicted as such in fanworks. In fact, anytime his eye glows, it always flashes blue and yellow.

* ParentalNeglect: The player causes this to happen during the True Ending [[spoiler:when the player doesn't tell Toriel or Asgore that their kid's still alive in a sense, trapped inside Flowey. It's made worse if you pick the option to remain with Toriel, living a short distance from where her son is perpetually trapped within Flowey. The True Ending has the player saving everyone else, but never giving Asriel's parents the vital information they'd want to know to even have the chance to try and save Asriel.]]

** Similarly, you'd be forgiven for thinking that the glow manifests as an emitted flame, when in-game it's depicted as [[GlowingEyesOfDoom a flashing pupil]] and the color never leaves the socket.

** On the musical front, a search of the game's music and its many, ''many'' covers might give you the impression that Asgore's battle theme is titled "Bergentruckung". It's not; "Bergentruckung" is the name of the song that plays ''before'' the battle, during the cutscene where [[spoiler:he destroys the MERCY button]]. His actual theme is just called "ASGORE".

** Because Undyne is one of the most human-looking monsters, fan-art often portrays her as a [[BuxomIsBetter busty]] AmazonianBeauty (though the busty part is just as often forgone), when she's actually pretty scrawny and flat-chested. Also, while in-game her hair consists solely of a ponytail (plus a sidelock during the Alphys date), many depictions of Undyne without her armor show her with a more feminine haircut.