just remembered that like a few years ago, i had this idea for a joke take on underswap called undaap (no clue how i came up with the name). i don't think i came up with that many plans for it aside from the fact that papyrus would've been a painter and his main reason for following the human around and showing up in different areas (like undertale sans) being that he's trying to get inspiration for what to draw next.
aside from that, the only other thing i really have about the au is this idea that just came into my head like a moment ago where like that moment where sans ends up making undyne stop for a few seconds in normal undertale (where he's sleeping behind the hot dog stand and undyne gets annoyed about it) is instead replaced with alphys accidentally running into like a fake tunnel painted by papyrus during the final chase and papyrus later acts like he did it on purpose to help out when in reality that was a complete accident