I've drawn Sans, Papyrus, and Frisk the most, but my style seems to consistently evolve for them all. Undyne and Alphys are also fun for me, but Alphys I draw really, really simply so as to avoid any real kind of snout, haha.
Haha, I have a personal AU in mind where Burgerpants works for the bunny shopkeeper up on the surface after they integrate into society. That might be a fun one. I like drawing Burg, too.
If you're into it, you could draw Shop Bunny and I'll do Burg. I always imagine him as much happier working for her, because I'm sure she's 1000% a better manager than Mettaton. ^ ^ Haha. Plus cinnamon buns!
Maybe she's behind the counter, and he's sweeping, or eating a cinnamon bun on his break.