Underswap Sans, ULCFan Wiki

Underswap is an AU where many of the characters' roles are swapped, as well as their personalities, though some quirks tend to stick in places, or are modified. Sans is the excitable, confident, extremely optimistic human hunter, while Papyrus is the laid back, protective bro following Chara

Underswap Sans, Wiki

Underswap Sans (Canon), Wiki

Canon Underswap Sans by Flybydogey101 on DeviantArt

Sans, Canon Underswap Wiki

Underswap and Fellswap - Sans and Frisk by WolfKIce on DeviantArt

Underswap Classic: Sans Fight! by Robby_Studio - Game Jolt

Sans/Underswap, New Undertale Fanon AU Wiki

Sans/Underswap, New Undertale Fanon AU Wiki

FW!UNDERSWAP SANS (OFFICIAL BIO), Wiki