Also known as: storyshift, shiftfell, storyswap
Undertale Alternate Universe created by the ut-storyshift blog on tumblr. It swaps characters' roles around, most notably placing Chara (Undertale) and Asriel in Sans (Undertale) and Papyrus (Undertale)' place.
It has since been combined with other popular AUs like Underfell and Underswap.