Who the hell is gaster

[Freaky Bob]

Ive seen a lot of people talking about gaster and i don't understand a damn thing. I know gaster is an old scientist that dissapeared because of his own creation but what does it have to do with deltarune universe? Can someone explain i'd apriciate that!

[Artificer]

(My information may be inaccurate due to my stupid dementia brain)
A theory I hear about Gaster's relevance with the Deltarune universe is that he creates the vessels you choose in the begging of the game, another part of the theory is that he is the voice that speaks to you in the begging.

Idk too much else since I have only started playing Deltarune and getting into it's theories and stuff 5 months ago.

[The guy from Ace Attorney]

Nobody knows yet. There's theories about Gaster and his relevancy to the plot of both games, but nothing concrete. All we have to go on are vague clues that may or may not relate to what we know of Gaster from Undertale. Some musical motifs, little bits of dialouge, and so on. The implication I believe, is that Gaster is the one who contacts both bonus bosses and drives them insane. As stated above, some players also believe he's the voice behind the "Vessel" creation at the start of Chapter 1 (The voice who discards the vessel at the end of the segment is implied to be someone else, again no clue who). As for the connection between both games, honestly I think it's better to assume that there is none for now, as that's what creator Toby Fox wants anyway.
So in conclusion, you don't understand anything, I don't understand anything, no one understands anything, chaos reigns, etc, etc.

[undarr]

You should probably watch some videos on it because saying everything here would cause a giant essay, but here are some examples of how Gaster is connected:

On the Switch version of Undertale there is an NPC called Clam GIrl that teases you about Deltarune 1 month before it released. Then their sprite turns into a monochrome version labeled as Goner Clam Girl before dissapearing with the sound effect the Gaster Followers and mysteryman (who is probably Gaster) use when they dissapear.

On the vessel creator sequence at the start of Deltarune, the voice that speaks to you speaks in the same spaced out with all caps way Gaster speaks in Entry 17. The vessel you create is labeled as "GONER" in the game files. And also the typer value (which is basically the number value in the game that decides in what font text will be in) is "666", a number that is associated with Gaster.

When you try to use your phone in the Dark World, a sound effect called "snd_smile" plays, which is the same sound that plays in Entry 17, speaking of that sound effect, there is a bunker in Hometown that plays "snd_smile" slowed by 666% when you get near it.

There are more things but I'm not typing all that.

[Oblivion Remaster EULA]

Me. I'm Gaster!

[JDLIXXD [SFM]]

I think hes the creator of Deltarune (yep, Deltarune is an experiment by Gaster or thats what i think)

[Amber110505]

There's a really good video called, "Who Dr. Gaster Is and Why That Matters to Deltarune" that explains just about everything.

[HenPlayer1]

"Beware of the man who speaks with Hands"

[queue]

he hit the pentagon

[S0me_Rand0]

A lot of the better answers are long so Ima make a short one. Gaster is some guy from undertale all you need to know for this game is he was "shattered through time and space" so he's in like 7900 places most likely. Anyways he's important for this game cause it's implied by some thingys that he's kinda watching the player and doin stuff. Oh also he made jevil insane and cut spamton off from mike so negative stonks

[sergame]

mysterious person that conveniently easy to tie to any crazy theory. but seriously speaking gaster was royal scientist in undertale that one day fell into his creation (probably core) and was shattered across time and space. there also alot of easter eggs that tied to gaster like "gaster followers" "room 269" "entry number 17" and many others, in deltarune his identity is alot more vague than its already is, there theories that he is creator of deltarune universe because one day toby fox twitter account was "hacked" by entity that was telling alot of strange things in capital symbols like gaster does and in the end he announced deltarune referring to it as "experiment". there also theories about gaster being puppet master due to the fact that mysterious person somehow contacting with secret bosses and makes them go insane but its all theories, in game there almost nothing about him except the starting scene and some other easter 𝗲𝗴𝗴𝘀