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UC Sans Ghost

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UC Sans Ghost
Type Ghost
Developer(s) Ymuy
Origin Undertale (AU)
Language(s) English
Sakura UC Sans
Release date December 26th, 2017

Content warning: Excessive swearing, glitching effects, mild flashing.

This article is about the Sans ghost for the Underchange AU of Undertale. For other ghosts of Sans, see sans (Disambiguation).

UC Sans Ghost is a ghost by Ymuy, of Sans from Ymuy's Undertale AU, Underchange. He is a rude and violent character, that swears frequently.

The ghost features an expressive shell, with many unique surfaces for various interactions, including animations. It also has a relationship system, where interactions and dialogue will change based on how the user treats Sans.


  • Relationship system, with a positive and negative route
    • Idle dialogues, mouse interactions, menu interactions, and more, will change based on how the user treats him
  • Has a currency system, where the user can earn “G” over time just by having the ghost open
  • Shop system, where the user can use G and purchase items
    • Items may be used infinitely once purchased
  • Gambling minigame, where the user can win or lose high amounts of G
  • Glitch mode

Relationship system

Sans's feelings towards the user are displayed on the main menu, via the pixel heart that appears in the bottom right corner. It is filled with an intense blue when his feelings toward the user are neutral. When his feelings towards the user are negative, it will fill with black. When his feelings towards the user are positive, it will fill with light blue.

Positive route

The user can increase their relationship with Sans by petting him if he is already at least a little friendly, giving him items, and by responding in certain ways to various interactions. Sans will grow to like the user, and some of his comments will change to be less violent. Though, he will never stop making them entirely.

If the user has purchased Sans's soul, they can also use the item and pet it for a large boost to friendship.

Negative route

The user can decrease their relationship with Sans by punching him, petting him when his relationship is already low, and responding in certain ways to various actions.

When the relationship is at rock bottom, as indicated by a fully black heart, Sans will dodge any attempts to punch or pet him.

Purchasing Sans's soul will decrease his friendship massively.


The user can earn G slowly over time, just by keeping the ghost open.

G can also be earned by playing the gambling minigame. G can be used to purchase various items.


The user can bet 1000G, 5000G, or 10000G. They will then have the choice between Red or Black, and Sans will draw a card from a deck. If the color of the card matches the user's choice of color, they win that much G. If the card does not match, Sans will take that amount of G from them. If the user doesn't have enough G, they will go into negative numbers.


Sans has a number of items available to purchase. All of them are a one time purchase, and the item may be used infinitely once obtained.

The following items are available:

  • Hotdogs! - 100G
  • Googly Eyes! 250G
  • Bones! - 300G
  • Crayons! - 500G
  • Ketchup! - 750G
  • Your Soul - 1000G

Note that the labels shown here are for the positive route. On the negative route they will be more aggressive.

“Your Soul” is listed as 1000G, but Sans will change the price on the user multiple times if they attempt to buy it. The final price of the soul is 100000G.


Each item that the user purchases will open up a unique interaction, complete with animations. Reactions to some items will change based on the user's relationship with Sans.


Sans will appear to eat the hotdog, and his comment on it will change based on his relationship with the user.

Googly Eyes

The user will place googly eyes on Sans's eyesockets, which will animate and wiggle around.

If the user's relationship is too low, Sans will dodge the attempt and not allow the googly eyes to be placed on him.


A regular, small, or extremely large bone will be chosen at random, and given to Sans. He will react differently to the different sizes.

If it is a regular sized bone, a dog will appear and leap to take it out of his hand.


Sans will ask the user what they are doing with the crayons. The user can choose to either draw on paper, or draw on his head.

If the user chooses to draw on paper, Sans will look at their drawing, and comment based on his relationship with them. If it is positive enough, he will keep the drawing.

If the user chooses to draw on Sans, he will decide to take a nap for a while. Double clicking his face while he is asleep will draw on him, and he will wake up and rub it off.


Sans will drink a bottle of ketchup, and comment based on his relationship with the user.

If the user's relationship is too low, Sans will refuse to take the ketchup.


Sans's soul will hover in front of him. The user may choose to give it back, pet it, or punch it.

Giving the soul back will increase his friendship a small amount. Petting the soul will increase friendship by a large amount, as Sans is relieved that he was not attacked.

Punching Sans's soul will kill him, and he will turn to dust. His soul will split in two, and the pieces that remain will fall on the ground. Double clicking them will give the user the option to reset.

When resetting Sans this way, he will still remember some details about the user.

Glitch mode

Click to reveal spoiler content.


UC Sans comes with the UC Undertale balloon, an Undertale themed balloon made specifically to suit him.