Got this idea after seeing this video and I'm gonna do almost all of them in which what Ben would look like in those au's

Undertale:

Underswap:

Underfell:

Outertale:

Underfresh:

Dancetale:

Horrortale:

Trainertale:

Fantasytale:

Inktale:

Underkeep:

Sugertale:

Nightmaretale:

Undertone:

Errortale:

Echotale:

Reapertale:

Storyshift:

X-tale:

Underland: