Basically, this is Undertale mixed with professional wrestling. I will be writing who I think should be who because of personality or just whatever, looks, emotions, all that.
Asgore: Vince McMahon: Now, I chose this guy because first of all, Vince is the owner of WWE, so I think that it would fit nicely into the role of Asgore. Of course, he's kind of a jerk, but... This Asgore wouldn't be as intimidating, and a little more well dressed, but beyond that their personalities fit.
Toriel: Linda McMahon: First of all, because she's the wife of Vince.. Second of all, because she is the kindest of the McMahons and would fit perfectly into the role. This version would be a little more tough (because this is professional wrestling, dangit!)
Chara: Stephanie McMahon: Everything works here. Stephanie is Vince's evil child who I would like to mention likes seeing literally everybody suffer. She likes watching people she doesn't like get decimated, and when things don't go her way, then.... Instead of just bloodlust, this Chara would be a lot more of a brat then normal 'I'm gonna kill you' Chara.
Asriel: Shane McMahon: This is about As-real as it gets. (noregrets) Shane is nicer than Vince and Stephanie, but is willing to go to high risk. This version of Asriel would be a little more violent, just as smart, but dresses less like a kid and more like a sports fan, with a cap and a t-shirt.
Sans: Enzo Amore: Now, this was hard for me, until I narrowed it down to Enzo. First of all, these two dudes are smaller than their partner, and looooove making puns. Enzo is great at public speaking and is always up for a good joke. Of course, if anything happens to his partner, he will go ballistic. This Sans would like to trash talk a lot more and would dress in a cheetah print jacket instead.
Papyrus: Big Cass: And this right here, this is Big Cass (Collin Cassady) and he seven foot tall! Enzo's close friend, Cass, is a lot taller than he is. Now this one, I am a bit divided on. Cass does like eating, but not spaghetti exactly... I can't find many others reasons he is like Papyrus, because he puts up with Enzo's jokes really well. This Papyrus wouldn't dress much differently, except for maybe some cheetah print.