"Charisk is probably one of the more disgusting things in the world..." They are totally not saying this out of Spite for Charas and because Lemon can't be with anyone but them. That would just be unthinkable.
What happened was that Papyrus accidentally absorbed the souls when trying to stop Flowey from doing so. Since he’s rejecting the souls, his body is constantly fluctuating. He’s trying to maintain his normal form while the souls are trying to change his body into something that can handle the excess power.
Flowey’s kinda in Papyrus’ death grip. Being so close to something so unstable pretty much caused him to melt into Papyrus as well. So they’re kind of an amalgamate in a way.
* Papyrus managed to pull himself together when he bumped into Asgore again. Asgore thought that Papyrus was sick so he offered him to recover in an empty room that he has in his house.
I have a question for the author. Papyrus at the beginning of Ask remembered the genocidal route. In the case, Sans, Alphys The Undying and Napstabot NEO were killed (and Asgore also inside the ruins). In the end, Papyrus dies, Chara killed Toriel in a one hit and Temmie was stabbed to death ... Chara gave his soul to Frisk? Is it a soulless pacifist route? And the shadow behind Chara with the L.O.V.E in the 19 was our shadow (Of the player)?
((The shadow was indeed meant to represent the player. And as of this run the player no longer has any input. And as for the results for Underswap’s genocide, I’d like to think it plays differently than Undertale’s, if you have Chara and Frisk as different personalities when they died anyway. But I wouldn’t say they’re soulless right now.))