So I came across a cool Undertale AU where it's mostly the same as in the game but- THEY ARE IN SPACE!
And also they have fancy re-designs and stuff. More info is on Outertale's tumblr blog. http://outertale.tumblr.com/

Tumblr: http://domino-bear.tumblr.com/post/133295112638/i-love-the-outertale-au-because-it-gives-me-an