History YMMV / UndertaleYellow

* SelfFanservice: Sometimes you may come across fanart of Starlo with a stronger build.

* GoddamnBats: On a pacifist playthrough, Sir Slithers can be a bit hard to figure out how to spare at first. [[spoiler:Unlike most monsters, you have to be a jerk to him by declining his offer to join you twice.]]

** Due to their similar appearances, some fans like to interpret Martlet and [[VideoGame/{{Deltarune}} Berdly]] being relatives, with Martlet being either his mother, aunt, or sister, and Berdly being her son, nephew, or brother.

* TooCoolToLive: Starlo, on the Genocide route. [[spoiler:He doesn't even get a proper boss battle, just a shootout that [[ZeroEffortBoss you can't lose]], with him being the only "boss" that [[SadisticChoice you're forced to kill.]]]]

** Is Mooch not allowed to drink Adult Soda due to [[VagueAge likely being a minor]], or does she simply go haywire whenever she gets her hands on that stuff?

* TheyWastedAPerfectlyGoodPlot: [[spoiler:Kanako is shown to be one of many monsters who were sent to Alphys’ lab after Ceroba injected her with the Determination. At the end of Axis’ fight on a Pacifist run, given how Ceroba’s motivations revolve around her daughter and thinking she’s still alive, you would think that the True Lab would be where she’s rushing to with Starlo in pursuit. Barring that, at the end of her FinalBoss fight, the idea of investigating what happened to Kanako is brought up. Other routes seem to indicate that the story would go in that direction, with part of Flowey’s boss fight in Neutral has Clover hear him in what’s implied to be him waking up there for the first time, and Martlet going into the lab in a flashback during a Genocide run. Instead, Ceroba unexplainably runs off to New Home, Clover decides to sacrifice themselves with the others reluctantly agreeing way too easily (Ceroba especially considering what’s been revealed), and Kanako isn’t touched upon again.]]

* TheyWastedAPerfectlyGoodPlot: [[spoiler:Kanako is shown to be one of many monsters who were sent to Alphys’ lab after Ceroba injected her with the Determination. At the end of Axis’ fight on a Pacifist run, given how Ceroba’s motivations revolve around her daughter and thinking she’s still alive, you would think that the True Lab would be where she’s rushing to with Starlo in pursuit. Barring that, at the end of her FinalBoss fight, the idea of investigating what happened to Kanako is brought up. Other routes seem to indicate that the story would go in that direction, with part of Flowey’s boss fight in Neutral has Clover hear him in what’s implied to be him waking up there for the first time, and Martlet going into the lab in a flashback during a Genocide run. Instead, Ceroba unexplainably runs off to New Home, Clover decides to sacrifice themselves with the others reluctantly agreeing way too easily (Ceroba especially considering what’s been revealed), and the plot point with Kanako’s fate is left unresolved.]]

* TheyWastedAPerfectlyGoodPlot: [[spoiler:Kanako is shown to be one of many monsters who were sent to Alphys’ lab after Ceroba injected her with the Determination. At the end of Axis’ fight on a Pacifist run, given how Ceroba’s motivations revolve around her daughter and thinking she’s still alive, you would think that the True Lab would be where she’s rushing to with Starlo in pursuit. Barring that, at the end of her FinalBoss fight, the idea of investigating what happened to Kanako is brought up. Other routes seem to indicate that the story would go in that direction, with part of Flowey’s boss fight in Neutral has Clover hear him in what’s implied to be him waking up there for the first time, and Martlet going into the lab in a flashback during a Genocide run. Instead, Ceroba unexplainably runs off to New Home, Clover decides to sacrifice themselves with the others reluctantly agreeing way too easily (Ceroba especially considering what’s been revealed), and the plot point with Kanako is left unresolved.]]

* TheyWastedAPerfectlyGoodPlot: [[spoiler:Kanako is shown to be one of many monsters who were to the Alphys’ lab after Ceroba injected her with the Determination. At the end of Axis’ fight on a Pacifist run, given how Ceroba’s motivations revolve around her daughter and thinking she’s still alive, you would think that the True Lab would be where she’s rushing to with Starlo in pursuit. Barring that, at the end of her FinalBoss fight, the idea of investigating what happened to Kanako is brought up. Other routes seem to indicate that the story would go in that direction, with part of Flowey’s boss fight in Neutral has Clover hear him in what’s implied to be him waking up there for the first time, and Martlet going into the lab in a flashback during a Genocide run. Instead, Ceroba unexplainably runs off to New Home, Clover decides to sacrifice themselves with the others reluctantly agreeing way too easily (Ceroba especially considering what’s been revealed), and the plot point with Kanako is left unresolved.]]

** Other than the final bosses, Axis on pacifist definitely qualifies. It takes a long time to bring down, its attacks hit decently hard, and some are very, very hard to avoid taking damage from multiple times, let alone at all. Granted, there are points where you can heal for basically free, but if there's a single non-final boss fight on the pacifist route where you'll die, it's most likely this one.

* ThatOneLevel: Prior to version 1.1, the Axis chase in the pacifist route was notoriously difficult, due to how fast they can catch up to you, leading to plenty of frustration from players on launch day.

** [[spoiler:Ceroba continued her husband's faulty research, and when Kanako naively asked to be used as another test subject, applied his Determination serum to her SOUL, which promptly cracked. Kanako was sent to Alphys's lab, and Ceroba stewed in her guilt for weeks before Clover came along and she deceived them into "rescuing" Kanako when she really just wanted their SOUL for more experimentation. While the story tries to depict her as being half-crazy with grief and hopelessly trapped in the SunkCostFallacy, her continued ranting that Asgore is no better or different than her sounds laughable in light of what happened to the Dreemurr children, and she ends the story either provoking a [[SuicideByCop Suicide By Deputy]] or moving on with her life with no acknowledgement of her mistakes beyond finally discarding Chujin's research.]]

* ShipsThatPassInTheNight: Although the two have barely interacted (outside of seeing each other in [[spoiler:the True Pacifist ending]]), people were quick to pair Dalv and Starlo together, likely due to their opposite personalities.

* AccidentalAesop: Just because you love someone, doesn't mean you should have [[UndyingLoyalty complete blind faith in them.]] [[spoiler:Much of what happened to Ceroba's family stemmed from the fact that Ceroba never once even ''considered'' that Chujin could have his faults or flaws. From believing it was Asgore's fault for snubbing his robot designs (despite several of the prototypes either flat-out not working or ''being legitimately dangerous even to monsters''), to having complete faith in the serum her husband was working on would work despite remaking it from incomplete research and her not being a scientist, and said serum being her husband's ultimate demise due to testing it on himself. The latter of which would ultimately cause her daughter to become a fallen down.]]

** Is Flowey nice since the game might be placed when he was good, or is he simply using you for his own personal gain? Upon the game's release, [[spoiler:it's revealed it's the latter, as Flowey organized all of the events to get Clover to Asgore when Clover kept dying on the path they would have taken with Toriel.]]

* SugarWIki/AwesomeArt: The game blends Undertale's iconic pixel-art style with smooth, expressive animations for most enemies and every major character. Add in a handful of impressive landscape shots and you've got a game that looks positively gorgeous from start to finish.
** Special attention goes to [[spoiler:Flowey's second phase in the Neutral route. His first was already delightfully terrifying even by this game's standards, but the second completely ''ditches'' the pixel-art for a Photoshop Flowey-esque finale. This time, however, his attacks are hand-drawn with animation reminicient of a traditional Disney movie, and Flowey himself has enough detail to look more like a painting than a sprite. It doesn't stop there, though; every time Flowey makes you shoot one of his petals, the animation style changes completely, from stop-motion to PS1-style models to a unique, VideoGame/{{Skullgirls}}-like form of traditional animation. The whole fight is a downright visual masterpiece in a game already full of fantastic visuals.]]

* BestBossEver: [[spoiler: Flowey's fight in the neutral run is often stated to be one of the game's strongest points, with Flowey's trippy attacks in the first phase ringing true to his Undertale characterization, and his second phase evoking the same feeling Omega Flowey did, with the various switching of vastly different art styles for each phase being a testament to the team's creativity. Add in the AwesomeMusic that is "BEST FRIENDS FOREVER" and "AFTERLIFE", and you've got one of the coolest bosses in any Undertale-related media.]]

** The secret boss fight against [[spoiler:Macro Froggit in the Steamworks is a bizarre battle that otherwise has no connection to the story and has a unique mechanic where the fight only ends once Clover collects all 5 frogs. Once the fight ends, an intimidating "Mega Froggit", a muscular humanoid figure with a Froggit head slapped onto it, will also approach Clover and hand over a sixth frog in a rather dramatic cutscene. Then the screen fades to white and Clover wakes up outside the now-locked room with the only indication that anything happened being a chest that has the Golden Bandana. It's as weird as it sounds.]]

* FandomSpecificPlot: Combined with FanficFuel; considering the [[spoiler:bittersweet nature of Yellow’s true pacifist route and Clover’s sacrifice]], and the ambiguous fate of the human souls with their coffins being open in ''Undertale''’s own pacifist route, writers (and a few artists) have taken up writing stories and drawing comics (mostly the former) of [[spoiler: Clover, post ''Undertale''’s true pacifist, finding themselves revived right after Asriel’s barrier destruction. Expect these stories to contain, in some way or another, Clover pushing and crawling their way out of their own coffin, meeting the ''Undertale'' cast, and eventually reuniting with ''Yellow''’s cast.]]

** Most people like to think that Kanako [[spoiler:became the spoon-like amalgamate that tucks you into bed in ''Undertale'', since an optional conversation with Ceroba in Steamworks has her talk about how Kanako wanted to be tucked in by her mother every night.]]
* FriendlyFandoms: With ''VideoGame/{{Deltatraveler}}'' given the fact that section 3 of that game released around the same time ''Undertale Yellow'' did.

* GoodBadBugs: The Golden Cactus is an item that, upon use, hurts you for 5 HP, and then for three turns afterward, heals you for 15 HP per turn. It's a risky, but powerful healing item, and you only get one... [[spoiler:However, the counter that tracks the turns that it can heal for is ''not'' reset after death or at the end of battle, meaning that if you die immediately after the first bite, you start the battle again with all three turns of healing ready for you.]] Okay, that's useful, but not ''super'' broken, right? [[spoiler:Except that by dying, you get it back in your inventory again. And if you use it while the previous one is still in effect, it ''extends the timer.'' Meaning you can build up dozens and dozens of turns of passive healing, and ''still'' keep it in your inventory when you stop abusing the glitch and finally take on your opponent for real, to use it again when you come to the next one.]] The bosses of the Genocide route aren't exactly a cakewalk even with this glitch, but it does significantly lower the difficulty into a more manageable range.

** One popular meme that resulted after [[spoiler: Clover's reaction to Axis' reveal that he killed the human with the Integrity SOUL is to compare it to the scene where [[Film/GuardiansOfTheGalaxyVol2 Ego reveals to Peter Quill that he put a tumor into his mother's brain]] due to the similar scenarios.]]

** "The Myth Of Consensual Copyright" / Let's Unpack the Music of Undertale Yellow [[labelnote: Explanation]] In December of 2023, Undertale Yellow's Soundtrack was hit heavily with Copyright Issues due to Materia Publishing (The Distribution Service that put Toby's works for Undertale and Deltarune under Copyright Protection on platforms like Youtube). This was in spite of the fact that Toby has always promoted the usage of his songs in Fanworks and Video Essays, as well as the fact that Toby gave permission to the creators of Undertale Yellow to use certain familiar Leitmotifs in their game. The fact that it's '''only''' Materia Publishing making such a big deal about the Copyright Claims has not been lost on the fans, as such memes about "Materia not giving Consent" and Copypastas in reference to Materia's opening Tweet about the Undertale Yellow Situation have been made of the subject matter because of it.[[/labelnote]]

** "hey clover, check out my new cut" / Bald Flowey[[note]][[Website/TwitterX Twitter]] user [[https://twitter.com/marsh_ber marsh_ber]] posted [[https://x.com/marsh_ber/status/1740441392244236509 a Discord screenshot]] of themself with a profile picture of a petal-less Flowey stating the aforementioned quote. The image quickly spread throughout the fandom due to the sheer hilarity of it, with many creating their own versions of the "Bald Flowey" sprite. Many artists have also taken to depicting the scenario in comic form, where Clover usually tries hard to hide their dismay when a Bald Flowey shows off his "cut" to them. Became AscendedMeme when an official artist [[https://twitter.com/AeroArtwork/status/1744098187734896969 posted sprites of Bald Flowey]]. [[/note]]

** Of the 3 final battles for each route, [[spoiler:the BattleInTheCenterOfTheMind against Flowey in the Neutral route is generally considered the [[BestBossEver most iconic]], namely for the sheer PsychologicalHorror of it all, the [[SugarWiki/AwesomeArt amazing]] [[ArtShift art shifts]] in the second part, the numerous [[ContinuityNod references to the route Frisk takes]] in ''Undertale'', and how much the scene works to develop the character of Flowey.]]

** Other than the final bosses, Axis on pacifist definitely qualifies. It takes a long time to bring down, it's attacks hit decently hard and some are very, very hard to avoid taking damage from multiple times, let alone at all. Granted, there are points where you can heal for basically free, but if there's a single non-final boss fight on the pacifist route where you'll die, it's most likely this one.
** While [[spoiler: Ceroba]] is necessarily hard on the Pacifist route as [[spoiler: the final boss]], she’s far from a slouch on the Genocide route. [[spoiler: Her attacks involve a multitude of blue and orange waves traveling near the entire length of the movable area, as well as red attacks which ''decrease your maximum HP'' if you’re unlucky enough to be hit by one. She takes it up a notch in her second phase by making it so ''the walls themselves'' not only do damage, but decrease your maximum HP like the red attacks. It certainly doesn’t help that she’s one of the most resilient bosses in the game in terms of HP, making it so that anyone who would attempt a Genocide run is in for a VERY rude awakening.]]

** [[spoiler: Chujin's Axis prototype ''murdered'' a human instead of capturing it thanks to a programming oversight, but instead of owning up to his mistake, he concealed the evidence, took the SOUL for himself and tried to get Axis approved for mass production -- only to present so many failed attempts that even [[NiceGuy Asgore]] got fed up with him. When he was finally dismissed from the Steamworks for his engineering mishaps, he again hid the truth from his family and turned his attention to the stolen SOUL, using himself as a test subject for his Determination theories. It's implied his experiments fatally damaged his own SOUL and resulted in a drastically shortened lifespan, leaving his family to grieve [[AllForNothing without accomplishing any of his goals.]]]]
** [[spoiler:Ceroba continued her husband's faulty research, and when Kanako naively asked to be used as another test subject, applied his Determination serum to her SOUL, which promptly cracked. Kanako was sent to Alphys's lab, and Ceroba stewed in her guilt for weeks before Clover came along and she deceived them into "rescuing" Kanako when she really just wanted their SOUL for more experimentation. While the story tries to depict her as being half-crazy with grief and hopelessly trapped in the SunkCostFallacy, her continued ranting that Asgore is no better or different than her sounds laughable in light of what happened to the Dreemurr children, and she ends the story either provoking a [[SuicideByCop Suicide By Deputy]] or moving on with her life with no acknowledgement of her mistakes beyond finally discarding Chujin's research]].

** "hey clover, check out my new cut" / Bald Flowey[[note]][[Website/TwitterX Twitter]] user marsh_ber posted a Discord screenshot of themself with a profile picture of a petal-less Flowey stating the aforementioned quote. Many artists have taken to depicting the scenario in comic form, where Clover usually tries hard to hide their dismay when a Bald Flowey shows off his "cut" to them.[[/note]]

* {{FandomSpecificPlot}}: combined with {{Fanfic Fuel}}
** Considering the [[spoiler:bittersweet nature of Yellow’s true pacifist route and clover’s sacrifice]], and the ambiguous fate of the human souls with their coffins being open in ''Undertale''’s route of the same name, it’s no wonder writers (and a few artists) have taken up writing stories and drawing comics (mostly the former) of [[spoiler: Clover, post ''Undertale''’s true pacifist, finding themselves revived right after Asriel’s barrier destruction. Expect these stories to contain, in some way or another, Clover pushing and crawling their way out of their own coffin, meeting the ''Undertale'' cast, and eventually reuniting with ''Yellow''’s cast.]]

* SelfFanservice: Sometimes you may come across fanart of Starlo with a stronger build.

** [[spoiler: Chujin's rush to prototype human-hunting robots was riddled with so many failed attempts that even [[NiceGuy Asgore]] got fed up with him, and his final iteration ''murdered'' a human instead of capturing it thanks to a programming oversight. Instead of owning up to his mistake, he took the SOUL and used himself as a test subject for his Determination theories, and it's implied his experiments fatally damaged his own SOUL and resulted in a drastically shortened lifespan.]]
** [[spoiler:Ceroba continued her husband's faulty research, and when Kanako naively asked to be used as another test subject, applied his Determination serum to her SOUL, which promptly cracked. Kanako was sent to Alphys's lab, and Ceroba stewed in her guilt for weeks before Clover comes along and she deceives them into "rescuing" Kanako when she really just needs their SOUL for more experimentation. While the story tries to depict her as being half-crazy with grief and hopelessly trapped in the SunkCostFallacy, her continued ranting that Asgore is no better or different than her sounds laughable in light of what happened to the Dreemurr children, and she ends the story either provoking a [[SuicideByCop Suicide By Deputy]] or moving on with her life with no acknowledgement of her mistakes beyond finally discarding Chujin's research]].

* HilariousInHindsight: Martlet (a blue bird monster who is a CrouchingMoronHiddenBadass) and Mo (a flamboyant sharp-dressed salesman) share close similarities to ''VideoGame/Deltarune'' characters Berdly and Spamton respectively, and both were teased before their respective ''Deltarune'' characters appeared, although due to the game's lengthy production time, they were only [[OlderThanTheyThink officially released afterwards]].

** Considering the [[spoiler:bittersweet nature of Yellow’s true pacifist route and clover’s sacrifice]], and the ambiguous fate of the human souls with their coffins in undertale’s route of the same name. It’s no wonder writers (and a few artists) have taken up writing stories and drawing comics (mostly the former) of [[spoiler: Clover, post undertale’s true pacifist, finding themselves revived right after Asriel’s barrier destruction, expect these stories to contain, in some way or another, Clover pushing and crawling his way out of his own coffin, meeting the undertale cast, and eventually reuniting with yellow’s cast.]]

* FriendlyFandoms: With VideoGame/{{Deltatraveler}} given the fact that section 3 of that game released around the same time ''Undertale Yellow'' did.

** Considering the [[spoiler:bittersweet nature of Yellow’s true pacifist route and clover’s sacrifice]], and the ambiguous fate of the human souls with their coffins in undertale’s route of the same name. It’s no wonder writers (and a few artists) have taken up writing stories and drawing comics (mostly the former) of [[spoiler: Clover, post undertale’s true pacifist, finding themselves revived also right after asriel’s barrier destruction, expect these stories to contain, in some way or another, Clover pushing and crawling his way out of his own coffin, meeting the undertale cast, and eventually reuniting with yellow’s cast.]]

* {{Fandom-Specific Plot}}: combined with {{Fanfic Fuel}}

* AlternateCharacterInterpretation: Is Flowey nice since the game might be placed when he was good, or is he simply using you for his own personal gain? Upon the game's release, [[spoiler:it's revealed it's the latter, as Flowey organized all of the events to get Clover to Asgore when Clover kept dying on the path they would have taken with Toriel.]]