Now, the main problem with making statements on ‘other worlds’ is that while they are implied to exist, there isn’t much left for us to analyze from.

What we know is more than zero. But only barely. I can literally list the references to other worlds on one hand. Knowing this … I’ll get work on making that list.

References To Other Worlds

Goner

The grayscale phantasm known to us as ‘Goner Kid’ that appears at Fun levels 90-99 talks mainly about a hypothetical ‘another world.’

* Have you ever thought about a world where everything is exactly the same…

* Except you don’t exist?

* Everything functions perfectly without you…

* Ha, ha.

* The thought terrifies me.

This, if we take it as canon, which I think we can, establishes that some (all?) other worlds are parallel worlds like this.

Riverperson

The Riverperson makes a reference to the ‘other world,’ telling us to beware a man from it.

* Tra la la.

* Beware of the man who came from the other world.

Interestingly, they use the exact same terminology to refer to Gaster, which is what fuels theories that link Dr. Gaster to ‘another world’.

* Tra la la.

* Beware of the man who speaks in hands.

Alphys

During the quiz show with Mettaton and Alphys, if in the last question Frisk responds ‘I don’t know,’ Mettaton and Alphys have an … interesting exchange of dialogue.

Mettaton

Alphys

CORRECT.

DR. ALPHYS HAS A CRUSH ON…

THE UNKNOWABLE.

YOU SEE, ALPHYS BELIEVES THERE IS SOMEONE OUT THERE.

SOMEONE WATCHING HER.

SOMEONE SHE THINKS IS “CUTE” AND “INTERESTING.”

HELLO, THEORETICAL PERSON.

DR. ALPHYS LIKES YOU.

TOO BAD YOU ARE NOT REAL.

*DERISIVE LAUGHTRACK*

H-hey, I’ve done research about this!

There are alternate universes out there!

S-someday, maybe, I could meet them…

Combined with the Goner Kid dialogue, this implies that at least some, perhaps all of the other worlds are like this … ‘alternate universes.’

Chara

During the worst run ending, Chara will talk about how it is time to destroy this world and move on to the next. However, when we do destroy this world, there’s actually not much to do.

It’s hard to say if the game was going meta and that’s the end, if IC Frisk refuses to move on or if Chara was just using ‘the next world’ as a euphemism for death.

I would argue that, while Chara’s words may mean something, the wide variety of interpretations that could or could not be valid doesn’t really make them very useful … except that Chara helps us define what a world IS.

These are the references to ‘other worlds’ in Undertale. All of them. No many, huh? We really don’t have a lot to draw on … but we do have something we can use to measure what other worlds are.

What We Know

Other Worlds Are Distinct From Timelines

Now, one thing that’s interesting is the distinction that the game makes between ‘worlds’ and ‘timelines.’ They’re different. Chara helps us destroy ‘this world.’ Literally all of time ends … in this world.

But the implication here is that other worlds would be more or less okay. Even as Frisk devours timelines, other worlds seem to be untouched.

Other Worlds Exist Concurrently With This One

The implication of the Alphys encounter is that in the UT multiverse theory, other worlds exist next to each other in a way that makes it theoretically possible for one universe to look at the other. This means they must exist side-by-side, at the same time, and able to interact in theory.

Some (Maybe All) Other Worlds Are Parallel Universes

The implication of the Goner encounter is that other worlds exist that are intensely similar to this one, with a few small differences. It’s entirely possible that the ‘other worlds’ that Alphys hopes to contact all also have an Underground, for instance.

This establishes a baseline for what other universes likely look like, and that if we ever do interact with them, that they likely will not be radically different from our baseline UT universe.

Gaster

The implication of the Riverperson is that Gaster … Gaster came from another world, somehow.

Speculation

Now that we have that out of the way, it opens us up for speculation. There’s … really not much to be done here. We don’t have enough information to make firm conclusions. I don’t even necessariy agree with everything I am about to tell you, and some of these things contradict.

I do not care. I am not here to find the one perfect truth. I’ve given up on that. Instead, this is meant to list out all the possibilities that I can think of.

Sans And Papyrus Are From Another World

I feel pretty confident in this one. sans constantly mourns being unable to ‘go back’ in a way that makes it clear that he is not actually talking about the surface. Plus, we must keep the fact that sans and PAPYRUS canonically came ‘out of nowhere’ into this world in mind.

In my mind, this gives speculation that sans and PAPYRUS are indeed from elsewhere strong ground. And that raises another theory …

The Mysterious Machine Is Linked To The Other World

The broken machine in sans’ basement is strange and doesn’t quite seem to have purpose. Why is it there? Toby once said on his twitter, and I’m paraphrasing … ‘There’s no better outcome. Neither of them could fix the machine no matter how hard they tried. No one can.’

If PAPYRUS and sans are indeed from another world, both the purpose of the machine and the people who tried to fix it come as a matter of course. sans and PAPYRUS, either independently or together, trying to fix what broke … and maybe, maybe … return home.

Gaster Was Thrown Into This World By His Accident

One popular theory is that the ‘old world’ was fractured, broken, maybe even destroyed by Gaster and his experiments.

The idea here is in falling into his creation, the world in which Gaster existed was … nulled. People point to Goner Kid as an example of what may have happened to him and suggest that rather than simply dying that perhaps Gaster was retroactively unmade. Memory of him eroded. Accomplishments forgotten. Influences lost.

The idea is that a new world without Gaster was ‘created’ by his experiments and now he lives, broken, in its shadow. But there are some problems. The fact that the ‘Core’ exists, for example. Was Gaster really erased from this world …?

Gaster Traveled To This World By Choice, Accident Is Different

This is what I believe now.

I think that Gaster is an intradimensional traveler that came to the world of Undertale. He came, like sans and PAPYRUS, to a world in which he did not exist. Before he was royal scientist, before he was anyone. That he only became Asgore’s royal scientist after he already came from another world.

If everything, his accident, his achievements, came after he visited this world, it would explain why his influence seems to persist. Perhaps his accident only scattered him across space and time … without erasing his prior influences on this world.

While it is true that we do not hear him talked about by any of the monsters, we ALSO don’t hear any of the monsters talk about Chara until we already know their story. So that doesn’t actually prove they have been erased from time, does it … ?