Various Old Men Within 👴💅

While I was high off my ass my druggie brain gave birth to two au versions of the old bastard man that are now additional optional encounters but before I get into them they're variants of

This Profile's (Main) Gaster
Sci Cult's just had a blog post and no other mentions anywhere lol

Sad wet old man to malicious(?) lump pipeline: his entire timeline plus that of his CORE (another option--requires going to his origin world--functions as a killswitch as it will actively annihilate this old idiot as soon as he enters the CORE facility) can be found in this blog post.

"Science Cult" Gaster

Wherein rather than gradually spiralling into major depression after the accident that killed a techie and irrepairably damaged him, he instead gradually went through the eccentric old scientist to madman bent on world destruction pipeline instead. Copy-pasting things from my blog,

◘ Pre-Erasure.
 ◘ A mystery science cult leader along the same vein as Pythagoras. The Followers will be coming into play with this one more-so than the blog’s flagship a**hole.
 ◘ He has two notable times one can interact with:
     • Prior to discovering that the world they are in is a game, wherein he is a mad scientist but not an outright antagonist. He’s actually nice! Just eccentric.
     • Until after discovering that the world they are in is just a game, at which point he starts to go off the rails. His Followers, well, follow suit. Their group could be likened to video game bosses while the BBEG(aster) works on changing and twisting and corrupting their world to try and gain the attention of whatever is behind the code their world runs on. Clearly a villain arc ending in his erasure but not-quite-there-yet.
 ◘ Not related to the skeletons.
 ◘ A wight.

When his creation is ultimately turned against him and his Followers, a failsafe kicks in. Everything is simply data, including himself and his sycophantic allies. Gaster created backups

So, while they are ultimately erased from their timeline (back up copies of lines of code, obviously, are not The Original Version of those lines of code), they do not cease existing altogether. It isn’t perfect, however. He did not have time enough to test it and make sure that everything was one hundred percent as it should be. The back ups weren’t updated to the very point of erasure, either–they were created shortly after he upgraded the original device that granted ability to see the world code to be able to receive and apply changes to that very code.

Fortunately, it’s easy enough to surmise that since the back ups were activated, that his original version was defeated. Further silver lining was the abject fact that no one within his timeline remembered who he nor his Followers were. Erasure is erasure. All memories of him and what he tried to accomplish were forgotten.

He and his Followers are now naught but ghosts, observing their timeline throughout its trials and tribulations caused by those other than them.

General appearance: that one sprite 

BSOD / "Crash"
A variant of "Science Cult" that succumbed to the same depression the guy a couple worlds to the left succumbed to, albeit after creating a world-corrupting doomsday device that he turned upon himself in a fit of "clarity." This ended up corrupting only his data, resulting in his prompt seeming erasure from his world and this monstrosity:

He can transform into the following sprite,