Bad Brother AU/History

Note: The plot in this verse of the BB AU partially follows the canon OG verse made by the creator of the AU, but some things does not follow the canon. Assume on this page "Sans" refers to BB!Sans and "Papyrus" refers to BB!Papyrus.
== Pre-SHAETALE ==
Sans is annoyed by the resets, but doesn't really give a fuck about them and just accepts it. He begins taking his anger out on Papyrus, being both emotionally and physically violent about it. He also does this as a source of entertainment. Even while at Grillby's, he manages to torment Papyrus. The abuse gets worse and worse, until one day...
== Debut Arc ==
The AU is introduced when Gaster visits it due to being suspicious of it. He knocks on the door, only to immediately allow himself in. He calls out to see if anyone's home, noting how there's empty beer cans everywhere, albeit piled in areas as if someone was attempting to clean up. Papyrus then debuts, peeping out of his bedroom, momentarily mistaking Gaster for Sans coming home. However, upon seeing Gaster, he panics at the sight of a stranger. Gaster attempts to calm him down and assures he's Papyrus's father from a different timeline. Attempting again to defuse the situation, Gaster tells him that he's must have had quite a party, referencing the beer cans. Papyrus, confused, is about to tell him his timeline's Gaster's been gone for a long time, but cuts himself off to answer Gaster; he corrects him and says there was no party, nor does he drink. At this revelation, Gaster becomes more concerned, now reassessing the scene with this new context, now noticing Papyrus looks tired, depressed, and has a bruise on his skull.
Now seeing a new alarming potential situation, Gaster becomes pissed. Worried, Papyrus asks if he's ok. Gaster notices that he's becoming scared, so he calms down to not spook Papyrus. He tells Papyrus he needs to come with him to his own timeline. At this, Papyrus stammers and refuses, saying he can't because he needs to clean up before Sans gets home. Gaster explodes the beer cans seemingly out of existence He apologizes and says he's suspecting of something going on. He resorts to forcing Papyrus to come with him and kidnaps him via picking him up and going through the portal, due to the latter's stubbornness. Papyrus increasingly becomes more panicked. He quickly denies of anything wrong, claiming everything just happens to be askew at the moment.