Unlikely Protagonists

Ok so I've been sorta struggling to come up with a paper topic this time around but I have one that I think would be good I'm just not sure if there is enough info and I can't find the common thread so hopefully y'all can help. My idea is to examine unlikely protagonists in some of the works we have read as well as some outside works. I was thinking of using Bod and his ghost family from Graveyard book, Jude the death metal rocker from Heart Shaped Box, and going outside the class for Dexter the a serial killer who only targets other killers. I know there's many more works that do this (Casper the friendly ghost, Shrek, etc) but I don't want to bring in too many. My worry is that I cant find the common thread that turns these characters that would normally be bad into lovable protagonists in each work. Any help would be appreciated! I'll try to help y'all out too! Thanks!