Quoted By:
The only pokemon that have both plot and backstory are cover legends. Everything else has either no plot, no backstory, or both. Of the cover legends, the only thing different about them is the theme they represent. None of the themes really stand out to me other than in a sphere of influence sort of way. I just can't favor any of them.
By the way, no, Mewtwo has a backstory, but no plot. It doesn't really do anything other than sit in a dungeon.
