Undertale Yellow secrets and glitches blog

UTY trivia #105: The dashes in the control information the first time you start the game are of varying lengths. The ones taken unchanged from Undertale are 6 pixels, while the ones that were changed for Undertale Yellow are 4 pixels. This is because of differences in the fonts they used.

UTY trivia #104: Martlet flies offscreen if Clover rides the minecart with her as a follower. When she returns, her line of dialogue mistakenly does not play her talk sound.

It is likely meant to appear if Clover interacts with a filing cabinet when it's empty, and is presumably not meant to appear when it is full. This is not how it works.

[Video description: A recording of Undertale Yellow where Clover carries out the below actions to get the described results. End description.]

If a cabinet is full and Clover is carrying a compound, the text incorrectly appears for cabinet 1 and correctly does not appear for cabinets 2 and 3.

If a cabinet is full and Clover is touching (distinct from carrying) a compound, the text incorrectly appears on all cabinets.

If a cabinet is full and Clover is not carrying a compound, they correctly pick up the compound from inside the cabinet (or sometimes pick up a different nearby compound from an astounding length. No idea how this is determined.)

If a cabinet is empty and Clover is carrying a compound, the text correctly appears on all cabinets.

If a cabinet is empty and Clover is touching (distinct from carrying) a compound, the text correctly appears on all cabinets.

If a cabinet is empty and Clover is not carrying a compound, the text incorrectly does not appear on any cabinet.

These strange conditions are due to Gamemaker handling instances in strange, unaccounted for ways.

(Interacting with a cabinet without picking up the compound Clover is touching is possible, but finicky. The most consistent way to do it is to use helium. This will sometimes stop working for unclear reasons, but doing it right after entering the room always lets Clover interact with the cabinet without picking the helium up.)

There is code in this interaction that is meant to set the word ASGORE to red. However, due to one line using the incorrect numbers (it says message_col[0][1] when it should be message_col[1][0]), this does not appear.

Mo has a full cameo

There's a cowboy segment with only this one reference, actually

There's an optional fight against the "zenith of cyberspace" with a remix of Retribution playing

Eric Whiteguy

UTY trivia #100: Telly-Vis's overworld NPC has some weirdness. The fifth line in their second interaction, "Oh you mean" is programmed to get interrupted by the sixth line for a gag. However, due to a bug caused by their first interaction having exactly five lines of dialogue, the fifth line of the first interaction automatically closes as well. This is sort of hard to notice through video but is obvious when playing. The third interaction onwards play as normal without getting cut off.

[Video description: A recording of Undertale Yellow. Clover talks to Telly-Vis in the overworld. They skip through the first interaction and let the last textbox reading "Ugh, this break can't end soon enough!" stay read out without skipping. The second interaction they skip through as well, only waiting on the part where Vis says "Oh you mean" and Telly interrupts with "Nuh-uh-uh! Off limits!!"

[Video description: A recording of the Undertale 10th Anniversary Stream. Frisk is in the long room of the Ruins and Toriel is saying, "Please remain here. It's dangerous to explore by yourself." Toby Fox is saying via TTS "If you noticed Toriel never ever uses contractions. This is her special superduper Homestuck typing quirk." End description.]

UTY trivia #99: At 1:11:59 of Day 1 of the Undertale 10th Anniversary Stream, Toby Fox talks over the only Toriel dialogue where she uses a contraction ("it's" instead of "it is") by saying she never uses contractions in her speech. However, not only does she use a single one there, she also uses a single one in a pretty unknown Undertale Yellow interaction.

UTY trivia #98: Jesus Christ

So: almost every time you enter any battle, your stats at the beginning of that fight get saved in a backup file. If you die in that battle and retry, it'll put you at the beginning of that battle with the same stats you had at the beginning: the stats it just saved. The only exception to this is Decibat, whose fight just does not back up those stats. This is almost definitely an oversight—the script used to start Decibat's battle is different than most other battles, the devs probably just forgot to include the saving bit in Decibat's unique script.

This means that if you press retry on Decibat's game over screen, you start back in Decibat's fight with the stats you had at the beginning of your last encounter. This is only for the "retry" button. The "continue" button uses your normal save, not your battle backup, so it works fine.

In the video, I showcase how retrying on Decibat interacts with HP. Casual players are pretty likely to run into this—Rorrim's mandatory encounter is right before a SAVE so they'll probably have lower HP when they run into him, and then they fight Decibat right after. (I mean, I thought Decibat was pretty hard... I died a couple times my first run...) If they encountered Rorrim while beat up and then died on Decibat, they'd retry with less HP than they started with. If you encounter any enemy while beat up and then retry on Decibat, you can see this yourself.

However, this affects more than HP. If you killed the last monster before Decibat, and then you die to Decibat, you lose that EXP—if your LV increased in that battle, your LV will go back down as well. So, level up from 2 to 3 in the encounter right before Decibat, then die and retry against Decibat, and you're LV 2 again. If you change your gear after that last encounter, you'll have the gear from before that last encounter equipped after you retry. If you did anything in that last encounter besides flee, dying to Decibat loses you whatever G you got in that last encounter. Decibat robs you.

UTY trivia #97: Clover can use three of the four ways to increase SP (soul speed) during the Ceroba battle—Sea Tea, Golden Coffee, and the Remember act all work, but Coffee Bean Ammo does not.

Sea Tea is coded to add 1 to the current SP, but Remember is coded to set the current SP equal to 1. This presents a unique edge case where drinking the Golden Coffee to make Clover's SP 3 and then using Remember actually lowers Clover's SP to 1.

Also, I put all the text differences in one place for easy viewing: