Nightmare Fuel / Undertale Yellow

This page contains unmarked spoilers for all areas of the game. You Have Been Warned.

"Let's entertain each other a while longer... After all, in this world... IT'S KILL OR BE KILLED."

Undertale Yellow, for the most part, is an upbeat, cheerful game. However, it does have its fair share of moments that are unnerving, creepy, or downright horrifying.

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• The entire Neutral Route ending. It starts with Martlet offering to let Clover live with her, giving them another chance despite the monsters they've killed. Clover accepts… and Martlet is promptly stabbed through the back by one of Flowey's vines. She dies thinking Clover betrayed her, which Flowey cheerfully points out. Flowey proceeds to berate Clover for messing up the mission, and when they try to attack Flowey, he simply reloads his save. Flowey then proceeds to kill Clover to try to absorb their SOUL and traps them in a nightmare world. But when Clover's SOUL resists being absorbed, Flowey explains Clover has had their journey several times before, but kept dying over and over (while showing images of Clover smashing into a wall of icicles, getting speared by Undyne, or disintegrated by lasers). Eventually, Flowey tampered with the Ruins switch, which set them on the path they are now. He then initiates a psychological horror-filled battle in which Clover cannot fight back, only run and survive. Flowey only stops after getting bored and admitting he knows neither of them are content with battling for all eternity. He then resets the timeline after telling Clover to get a different ending this time.
  • The first phase is no slouch in being an absolute horror storm. As the battle continues, the menu is constantly glitching out, fighting only leads to being forced out of the fight command, and using healing items leads to a similar result. The only thing Clover can do is ACT or spare to pass turns, and said ACT options that aren't some form of determined perseverance are creepy, being options that do nothing such as "Weaken", "Decay", and "Suffocate". Meanwhile, Flowey attacks with a horrifying onslaught of attacks, with depictions such as his face opening up in various creepy ways to fire attacks, human hands ripping off his petals as he screams in agony, or copies of himself being slaughtered to unleash something onto Clover's SOUL.
    • During your turn, the text ends up glitching out too, as while most messages are complete gibberish, a couple of them are at least somewhat legible, saying Clover is trying (and failing) to fight back, while another describes Clover attempting to cry, yet they have no eyes.
  • Whenever Flowey takes the appearance of different bosses, most of them are just glitchy messes that vaguely resemble the boss' shape. El Bailador, on the other hand, is much clearer and wears a positively haunting Slasher Smile during his attack.
    • Despite Dalv’s glitchiness, you can make out his face being blank except for a cold stare at you.
    • Starlo is heavily glitchy, with what seem to be roots growing from his face and a single flower in his hat to show who’s REALLY in control.
  • During the part of the battle where Clover has to avoid vines coming from the ground, at some point they leave the Underground portions of the map and travel through a dark hallway filled with distorted copies of Flowey, who plead for help, call for mom and dad, or just laugh manically; a gentle reminder that the entire battle is taking place in Flowey's mind. The final one Clover comes upon… well…
  Flowey: "what have I done?"
  • The scene after this is especially haunting: you're put in a place that looks like Snowdin with a distorted version of Snowdin's normal background music playing before encountering Martlet, though the fact that she's here at all after being killed and the fact that her dialogue box isn't showing her character portrait should be setting off some immediate red flags. As the scene continues, Martlet mentions the events prior to her death and offers to bring Clover back to Snowdin before…
  "Martlet": I'm so happy I found you!
  "Martlet": So happy I found you.
  "Martlet": I found you.
  ("Martlet's" face melts off and becomes a black void, which is then replaced with Flowey's eye)
  "Martlet": I F O U N D Y O U
  (A distorted version of Flowey's Evil Laugh plays alongside a horrible grating screech as "Martlet" melts before your eyes into a shapeless blob)
  • Before Martlet begins to hug Clover, there's a few frames where you can see Martlet with her eyes and beak as empty holes.
  • Let's go into more detail about Flowey's second phase. The foul flower appears massive, detailed, and wearing his trademark psychotic smile. The attacks are hand drawn and like before with Omega Flowey, the fight stops at certain points to change up attack patterns. Only instead of using the weapons of the human souls, Flowey grabs Clover and holds them while these differently styled petals spin around. The new phase is determined by what petal is hit and they’re all equally unsettling. One style features Flowey turning into a heart as blood cells and viruses float around. One is a paper scrap style. Another is an old school cartoon style where Flowey becomes a giant weapon firing bullet spreads. One turns Flowey into a giant ragdoll while ghostly hands try and throw nails. Another style is stop-motion where giant eyeballs try and attack you. And finally, there's an N64-styled Flowey that dances to crazed carnival music, while lanky humanoid Floweys crawl down from above to swipe at you.
    • The music is also worth mentioning:
    • specimen: patchworked sounds joyous and happy, unfitting for the situation
    • specimen: organic has the sound of a heart rate machine (which seemingly flatlines at the end) accompanied by a horrid whirring noise that alternates between left and right speakers
    • specimen: paper sounds like something reminiscent of the Sonic CD US boss theme
    • specimen: polygonal sounds like Creepy Circus Music
    • specimen: mechanical sounds good at the start, until halfway in, where the electric guitars sound like ungodly screaming.
  • There's also a small moment that stands out after Flowey gets tired of attacking Clover. The camera starts zooming in towards Flowey and after a bit, his eyes move away from Clover… and towards the screen, as if he's looking at you. It's subtle and only happens for a moment before the camera zooms out and Flowey starts talking to Clover again, but it's remarkably creepy considering there aren't any other moments where Flowey toys with the 4th wall asides from this, so it's easy to be caught off guard from it.
• The entire hidden Jigsaw Puzzle Plot about Axis's murder of the Integrity SOUL is probably one of the most disturbing things in the game, and has an implied level of graphic violence beyond even anything from Undertale.
  • (Neutral Only) If you discover the secret room in the Steamworks, you'll find an inhabitant how who hid themselves away to continue their experiments in secret, out of protest against the decision to fire those that worked there, and to keep themselves safe from the roaming robots. The room itself has nothing of note except a book titled "Mysterious Of The Underground".
    • The first entry is pretty light, simply talking about the out of order arcade cabinet in the Oasis Valley Cafe, and its "unpleasant" contents… though it becomes less lighthearted when you realize it's a Shout-Out to Polybius.
    • The second entry, which is a bit more chilling, tells of a father whose child ventured into an area beyond the fences, and before finding them, described themselves in a daze, and seeing… nothing.
    • The third entry, titled "The Phantom SOUL", however, is outright nightmare-inducing, as it goes into detail describing what happens to any human child that falls into the Underground, simply stating that they are "collected". But the real horror comes later, when it goes on to tell the story of a human child that was suddenly spotted in Snowdin, only for them to flee to Waterfall, and this being the last time they were seen…only for their SOUL to mysteriously show up in the deeper parts of Waterfall years later. This entry is so disturbing to Clover, they immediately put the book back saying nothing further, and if they later do a Pacifist Route, and make their way around Ceroba's mansion…
  • (Pacifist Only) While nothing scary pops up, if you decide to check the grave of Chujin behind Ceroba's house,^note the back side to be more specific you'll find a hidden tape with no label on it. If you decide to view it in the hidden basement, you'll see Chujin narrating again, only this tape's contents contains things you wish you never found… because it's ripe with him sharing the hidden details surrounding the "The Phantom Soul" book entry, revealing that Axis had killed that human even though Chujin wanted to apprehend them (who is all but said to be the one with the Integrity SOUL). This becomes even more disturbing when you realize that Axis was being built before the attack, indicating that Chujin was planning on dealing with humanity using them from the start. While Chujin was absolutely disturbed at the sight he saw, and even briefly considered stopping what he was doing, the attack simply gave him more motivation to go on with it, now having proof that Axis was indeed capable of what he originally intended. Also, with what Axis says on the Genocide Ending, it might have been possible that its programming thought that apprehension simply meant killing the human… how thoughtful.
  • Axis' death in the Genocide Route. After a fight that mostly consists of you futilely shooting his garbage lid shield, he explains everything, including how he was the one to kill a human who came before Clover. Clover fucking loses it, and gains several LV while Axis watches in stunned horror. Then, you shoot a Big Shot at his shield, knocking it out of his hands before preparing a longer and far, far more brutal one to finish him off with. All the while Axis helplessly begs that he didn't want to do it and tries to convince you to spare him to no avail. You demolish him with a massive laser from your SOUL, and all that's left are a pair of bisected robotic halves just barely connected at the bottom to the wheel. It also splits open further as it falls. You Bastard!
  • With specific Fun values, some of the Dark Ruins pillars can have drawings depicting Axis, the Integrity human, and a human SOUL surrounded by some sort of splatter. Notably, the pillar with the human drawing is damaged where their face would be, raising the possibility that Axis blew the kid's head off.
• After Axis' death, Clover's thoughts become available to the player as they walk further into the Hotlands. At first it starts off somewhat mundane with "Need to find an exit." But when you get to the Hotland Heights and see Martlet's feathers on the ground, they think, "An enemy is nearby. No loose ends." And once you climb the stairs to confront her, all Clover thinks is "Let justice be done."
• Martlet's death after her Genocide Route boss fight. Prior to the fight, she injects herself with determination to give herself an Undyne-the-Undying-like power boost. At the end of the fight, she starts melting, panicking and begging for help, before ultimately perishing.
  n-NO!
  PLEASE!
  WHAT DO I DO!?
  STOP!!!
  SOMEONE!
  H E L P M E . . .
  • Martlet's transformation into the Zenith of Monsterkind is only marginally less creepy to watch as her body shifts around as the Determination courses through her. At one point, her sides tear open to release her giant wings.
  • The game doesn't get any better after that. Flowey appears after Martlet's death, angry with Clover because he knows the Underground will fully pull up its defenses because of the human's actions. After he accidentally reveals he wants the human SOULs for himself, Clover overwrites his SAVE, preventing him from attacking or fleeing. Upon realizing his power is gone, Flowey finally shows his true colors, spitting out his hate for Clover and only feeling satisfaction each time they died. He tells them no matter what they do, they die, and laughs manically before Clover silences them with several bullets to the face. By the way, you're also treated to a lovely, lovely animation of his ruined corpse flopping to the floor, complete with a thud sound. Sweet dreams.
  • Checking the coffins in the castle just prompts a "..." from Clover.
  • Asgore's death is only slightly less gruesome, in that Clover kills him in one shot. But you are treated to the lovely sight of Asgore's eyes and mouth opening wide from the pain before his body turns into dust. And the shot was so powerful that it obliterated the throne and the wall behind him, while also scorching the flowers beneath his feet.
• In the second flashback during Ceroba's Pacifist fight, we're treated to a scene where Kanako convinces her mother to inject her with Determination in an attempt to continue Chujin's legacy… only for her to immediately pass out and "fall down" right into her mother's arms. Ceroba's reaction makes it clear how horrifying this is from her perspective, especially since everything was just fine only moments before. No wonder she snaps at the route's end.
  • This is only exacerbated by a lovely hint of Fridge Horror; Ceroba sent Kanako to Alphys after she'd "fallen down". She believes that in her current state, Kanako is practically dead already, but anyone familiar with Undertale's True Pacifist ending will know that the truth is so much worse.
• It's incredibly disturbing when it's revealed that Martlet, the monster that is always there to support Clover, and likely the one they're the most comfortable being around, due to their kind-hearted and empathic nature, could have turned herself into a powerful force of nature and massacred them at any point if she chose to.
  • The Neutral Route makes it very abundantly clear that during the entire time she spent with Clover, acting positive, being supportive, and staying by their side, in the back of her mind, she was contemplating whether or not she should use the serum on herself, and kill them on the spot.
• While pretty much everything about the reveal of what Ceroba is really up to on a Pacifist run is unsettling, the worst of it comes when you watch Chujin's tapes in her old house. All the videos show is static over a sillhouette of Chujin, with his Scary Shiny Glasses being the only distinct feature on his face you can see.
• Like with Undertale, there's a new set of FUN value events, and while none have to do with Gaster, some of them are rather disturbing.
  • If you have the right FUN value, then when going through Snowdin, you'll end up in a mystery room with a monster named Jane, who talks about how monsters have been randomly going missing. Talk to her a second time, and she remarks that someone has to be responsible. And the moment you leave the room, you can't come back.
  • Another version of the hidden Snowdin room will instead have a unicorn-like monster named Wanda . She claims to have ran into the woods to spite her (possibly imaginary) boyfriend, and will spout off a whole lot of other Manic Pixie Dream Girl things that seem to reflect very poorly on her mental state, and it's unclear whether she was like this before she ran away or whether the forest is actively making her go insane. Like with Jane, the only option the player has is to leave her and be unable to return, so you probably condemned a mentally unwell monster to be lost forever.
  • In another FUN value easter egg, the abandoned Steamworks room that Axis tosses the player into will have the staticy face of the Ice-E mascot grinning on the monitor (which normally otherwise just shows plain static). If Clover approaches, it will Jump Scare them with a distorted shriek and then disappear. It's a pretty clever culmination of all the little Five Nights at Freddy's references in the room, but it's incredibly unnerving. Especially as the monitor is not supposed to show anything, as it's not connected to any cameras.
  • Another FUN value can have the TV in Ceroba's basement activate on its own in the overworld itself as another sort of jumpscare, showing an image of Chujin's aforementioned silhouette as creepy static plays, before turning off. Even worse, the initial build of the game accidentally allowed for this to also happen during the cutscene in the final battle where Ceroba injects Kanako, making the already tragic scene turn terrifying instead.
• Bits and Bites is, naturally, abandoned along with the rest of UG Apartments on a Genocide route. But you aren't alone, as the shop has a lone humanoid figure just... standing there in the dark, watching you. Whoever or whatever this thing is, nothing in the game acknowledges its presence or gives it any context.

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clover would like to cry but they have no eyes