Something to note is that Marauder isn't too far off with his statement about it being based on "Undertale AU #563" aka Xtale (that's why it's called the "X-event) the creator's original AU that was made for their fan series (Underverse)
(The maker herself)
The Xtale characters were just the main villain or whatever but at somepoint the maker realized that she couldn't do too much with a series where it's just "go to this AU and then this new Sans joins the team" this epiphany came when they had to make the Outertale episode.
You see the other two aus (Fell and Swap) had something that differentiated them from the original Sans but Outer had literally nothing other then he was in space so Jael (the maker of the series) killed him off and decided to turn one of the characters evil for no reason. (Ink Sans the one in the photo, Week 2 of the mod) to reboot the whole series.
Anyways after that she went onto making her original AU be even more of the focus with making a prequel series explained the universe n' shit, this is the point where I dipped cuz the direction being turn to this weird AU was pretty jarring mixed with how poorly handled the ending was, that and I wasn't (and still am) not a big fan of the design for the AU.
That's the extent of what I know when it comes to Jael's stuff, I only checked back to see what was going on with Underverse and I watched abit of the "420K subscriber special" which was pretty gay, it was literally just a PSA about not stealing her shit which is the weirdest thing you could do for a special.
Okay about to the topic of the thread, aside from the horrible note spam I find it really funny that they used Sans talking sounds for Week 2 which is meant to be super serious and stuff. (it's based on the already brought up awful ending)