History VideoGame / UndertaleYellow

** One of the {{Flavor Text}}s in Axis' fight is "Death by metal & magic." This likely alludes to Mettaton EX's theme, "Death by Glamour".

Announced only a few months after the release of the original game, the project started on February 4, 2016 after Toby Fox allowed it to be greenlit. A [[http://gamejolt.com/games/undertale-yellow/136925 demo]] was made available on Gamejolt in March of the same year, with the mod (finally) releasing on December 9, 2023, available to download [[https://gamejolt.com/games/UndertaleYellow/136925 here]] on Gamejolt.

* CallForward: [[spoiler:One of the flavor text narrations for the Axis fight on a Genocide run is "In your way."]]

** Numerous characters from ''Undertale'' such as Undyne, Alphys, and Mettaton are mentioned directly or indirectly, even if not shown.
** There's a list of award-winning Underground scientists in the Steamworks, among which is Chujin, but one accolade appears to be entirely obscured, recalling the numerous hidden references to Gaster in both ''Undertale'' and ''Deltarune''.
** Despite all the horror [[spoiler:Flowey puts Clover through in the final battle, he reveals at the end that everything is in his head and that once his plan reaches fruition, he'll manage to finally gain a physical form that will allow him to achieve what he always wanted, and that Clover will be there to watch]].

** The detention room that Axis tosses you in the Steamworks has a suspiciously familiar table that features [[Franchise/FiveNightsAtFreddys a computer, a table fan, and a phone]], and interacting with the computer will prompt a quote about how nice it would be to have security cameras that monitor robots in the Steamworks, but that they were never installed. You even escape it through the vents, not unlike how the animatronics can attack the player in ''VideoGame/FiveNightsAtFreddys2''. [[spoiler:Unsettlingly enough, the room even has a jumpscare (itself featuring none other than the "Purple Guy" ICE-E's P"e"zza mascot from ''VideoGame/{{Deltarune}}'') that shows up on the allegedly nonexistent security cam if the game has a FUN value of 16-19.]]

** One of the {{Flavor Text}}s in Axis' fight is "Death by metal & magic." This likely alludes to Mettaton EX's theme, "Death by Glamour".

** The [[spoiler:carnivorous plants that Flowey attacks with in his final battle closely resemble [[Franchise/SuperMarioBros Piranha Plants]], right down to attacking out of pipes]].

** Dalv's dialogue before and during his boss battle where he acts as if he's met Clover before and thinks they want to "finish the job" makes more sense after learning that [[spoiler:a previous human had attacked a monster in Snowdin during Chujin and Kanako's visit, with some hints strongly suggesting that Dalv was that same monster]].

* EleventhHourSuperpower: [[spoiler:During the FinalBoss of each route, Clover's SOUL gains the shooting ability of the yellow SOUL from ''Undertale'', giving Clover a means of attacking during the enemy's turn. Doubles as AntiFrustrationFeatures as the player no longer has to decide between attacking or healing during their turn, which is a welcome change when all of the final bosses have very difficult patterns.]]

* AdaptationalVillainy: In ''Undertale,'' the only description for the Old Tutu and Ballet Shoes in Waterfall was that the former is covered in dust and the latter made Frisk feel "incredibly dangerous" when putting them on, [[AmbiguouslyEvil leaving it ambiguous whether Integrity killed monsters maliciously or out of self-preservation.]] Outside of that, they help Frisk out during the Neutral and Pacifist routes like the other souls. In ''Undertale Yellow,'' [[spoiler:they're firmly in the malicious category. They almost killed Kanako and Dalv, [[WouldHurtAChild the former being a young child]], and is overall described as violent by the other characters, ultimately being killed by Axis in Waterfall (albeit unintentionally). Their soul continued to cause problems even after their death, getting Chujin killed when it kept refusing to fuse their souls together, and being indirectly responsible for Kanako's fate as an Amalgamate.]]

* AllForNothing: In the flawed pacifist ending [[spoiler: Martlet's idealism]] is smashed to pieces when [[spoiler: all of her efforts to keep Clover safe and find a happy ending are met with reality when Asgore kills Clover.]]
** This happens again in [[spoiler: either]] pacifist ending as [[spoiler: Flowey gives up on getting what they want from Clover, allowing their hundreds of attempts and resets to go to waste as the flower lets the time continue, waiting for the next human in the hopes they'll do better.]]

* AndIMustScream: [[spoiler:The entire Neutral Route Flowey battle, which takes place after he kills Clover and absorbs their SOUL, with them trapped in his mind and trying to avoid being completely absorbed. The battle even has somewhat similar and terrific flavor text: "Clover would like to cry, but they have no eyes"]]

* AnimationBump: The game's sprite work is much more fluid and detailed than Undertale's, due to having multiple artist and animators working on it. Additionally, climax fights will always be much more painstakingly animated than most of the normal bosses in the game. [[spoiler:Ceroba on the pacifist path, Martlet on the Genocide path, and ''especially'' the fight inside Flowey's mind are some of the standout examples.]]

* CruelMercy: [[spoiler: Dalv is the only boss you can spare without aborting a Genocide run, and he'll even call you out on leaving him the only one alive.]]

* CurbStompBattle: [[spoiler:This is how the Asgore "fight" plays out at the end of a Genocide run, just like in Undertale proper.]]

* DramaticIrony: [[spoiler:Ceroba senses that her daughter is still alive even after being sent to Alphys due to her state... With the location being the Lab, where at this point Kanako is most likely part of an Amalgamate.]]

* KidsRaidingTheWineCabinet: The saloon in the Wild East serves "Adult Soda", but Dina refuses to serve Clover any. Clover can snag a bottle anyways from a trash can in New Home on a Pacifist run, or they can take one from a more spiteful Dina on a Genocide run. It notably doesn't get Clover drunk or have any negative effect on them, stated to just "taste like water".

** There's a suspicious arcade cabinet in Oasis Valley that's a clear ShoutOut to the ''VideoGame/{{Polybius}}'' urban legend, with a FUN value of 65-69 causing an agent to show up and take notes on it.

** The Pacifist route final boss, [[spoiler:Ceroba, is overtly Japanese in aesthetic in an otherwise SpaghettiWestern inspired game, and (like the other final bosses) utilizes the ShootEmUp mechanics characteristic of the Yellow Soul, which might bring to mind the BulletHell genre codifier itself, ''Franchise/{{Touhou}}''. The battle theme that accompanies her second phase is also very reminiscent of Creator/{{ZUN}}'s musical style. This is also the case for the Mew Mew Love Blaster arcade game]].

* AndIMustScream: [[spoiler: Entire Neutral Route Flowey battle. It even has somewhat similar and terrific flavor text: "Clover would like to cry, but they have no eyes"]]

** Many of the attacks of [[spoiler:Macro Froggit]] put resemble other video games. One puts you on a road while cars (with frogs driving them) drive past, resembling ''VideoGame/{{Frogger}}''. Another has a frog on an Arwing from ''VideoGame/StarFox'' shooting at you, wearing a headset that makes him vaguely resemble Slippy. Yet another has you attacked by a humanoid frog wielding a sword, resembling Frog from ''VideoGame/ChronoTrigger''.

** The Pacifist route final boss, [[spoiler:Ceroba, is overtly Japanese in aesthetic in an otherwise SpaghettiWestern inspired game, and (like the other final bosses) utilizes the ShootEmUp mechanics characteristic of the Yellow Soul, which might bring to mind the BulletHell genre codifier itself, ''VideoGame/{{Touhou}}''. The battle theme that accompanies her second phase is also very reminiscent of Creator/{{ZUN}}'s musical style. This is also the case for the Mew Mew Love Blaster arcade game]].

* RoleReversal: When playing through the Steamworks on a Genocide route, this is utilised in a dark manner in contrast to the Pacifist/Neutral route.
** [[spoiler:Instead of Clover tumbling down a trap door in their first confrontation with Axis, the robot uses that same trap door to make his escape when he realises just how big a threat the human child is.]]
** [[spoiler:Likewise, instead of Axis chasing Clover through the facility, Clover instead chases Axis through the hallways.]]
** [[spoiler:The Pacifist/Neutral route had Axis giving Clover a bin lid as the equivalent of a weapon to exploit the loophole of his programming. In the Genocide route, however, he uses that bin lid to defend '''himself''' from Clover's onslaught.]]

* SkippableBoss: [[spoiler:If you exhaust your kills in the Dark Ruins before reaching the bridge where you fight Decibat, he won't appear. Similarly, if you exhaust your kills in the Dunes before reaching the mountain, then you will not get to fight El Bailador. These do not abort your Genocide run, though.]]

* InfinityPlusOneSword: For ammo, the Friendliness Pellets, which are acquired late into Steamworks if Ceroba isn't with the player [[spoiler:(though at that point, there's barely any fights to test them out on)]] or after [[spoiler:the Ceroba fight]] on No Mercy Route, boasting 11 attack points, only rivaled by Silver Ammo's criticals. For armor, there is the Golden Bandana, acquired for bringing all the hidden golden items to yet another hidden room in Steamworks, boasting an amazing 12 defense points. Unlike the pellets, it is available on all routes, [[spoiler:though the BonusBoss protecting it does not show up on No Mercy]].

* CycleOfRevenge: [[spoiler: When Clover confronts Asgore in the Genocide ending, he tells them that their actions have ensured the war between humans and monsters will never end, and that many people on both sides will die as a result.]]

* DramaticIrony: [[spoiler:Ceroba senses that her daughter is still alive even after being sent to Alphys due to her state... With the location being the Lab, where at this point Kanako is most likely part of an Amalgamate.]]y

* ScrewThisImOuttaHere: [[spoiler: Most of the shopkeepers pull this on a Genocide run, with the exception of Dina, who simply refuses to sell to you, and Vendy, who is likely immobile, but is afraid of Clover and gives items for free.]]

* AdaptationalVillainy: In ''Undertale,'' the only description for the Old Tutu and Ballet Shoes in Waterfall was that the former is covered in dust and the latter made Frisk feel "incredibly dangerous" when putting them on, [[AmbiguouslyEvil leaving it ambiguous whether Integrity killed monsters maliciously or out of self-preservation.]] Outside of that, they help Frisk out during the Neutral and Pacifist routes like the other souls. In ''Undertale Yellow,'' [[spoiler:they're firmly in the malicious category. They almost killed Kanako and Dalv and is overall described as violent by the other characters, ultimately being killed by Axis in Waterfall (albeit unintentionally). Their soul continued to cause problems even after their death, getting Chujin killed when he tried fusing their souls together, and being indirectly responsible for Kanako's fate as an Amalgamate.]]

* Retcon: While the game does its best to be as canon as possible, there's inevitably some contradictions:
** In Undertale, it's indicated that a long time has passed since the last human fell into the Underground before Frisk did, to the point where the majority of monsters don't recognize them. In Undertale Yellow, flashbacks and various dialogue implies Clover jumped into the Underground around a year or two before Frisk at most, with Integrity falling into the Underground a couple years before that.[[note]]Also, while we're not given an exact time frame, the Amalgamates are implied to be recent since Snowdrake is still a homeless teenager by the time Undertale takes place.[[/note]]