A HeadCannon in stories I love is Sans being friends with Chara and Asriel before they died. Makes it more heart wrenching when applied to something new. Your best friend how you may or may not be on good terms with us back from the dead along with your other friend who is soulless they want to be best friends again, they want you to join them in killing everyone you know, they hurt you, you hate them but you can’t stop thinking of before and how you failed them once and now you can make up for
Wonder if that could branch off into the idea of Something New Sans also being the Sans from Handplates.
Maybe in that timeline, Papyrus and/or Sans were allowed (or secretly met) one or both of the Royal Children, and perhaps discovering Sans/Killer and Papyrus’ existence and how Dr.Gaster treats them and why he does that is what further encourages Chara and Asriel to go through with their plan to find six souls to free Monsterkind.
Because now not only would they be freeing every Monster, but maybe they can free their friend(s). Chara seems like they’d be willing to sacrifice themself even more for that.
Timeline may not make any sense but hey it’s fanfic concept of aus 🤷
