Back when we often played superhero RPGs – mostly Mayfair’s DC Heroes and Green Ronin’s Mutants & Masterminds – we always made up a comic book “universe” for the adventures to take place in. This included a lot of other superheroes which we created and made stats for, but never actually played. My favorite among them is Duplica, the Multiple Girls.
Duplica could multiply herself into many versions of herself, much like Marvel’s Jamie Madrox. Every version of her came from a different concept universe, and had a different personality. When she would send the Multiple Girls away, a different girl would stay behind on this Earth.
I think the multiple personalities of the character would be fun to play, as well as examining what takes place in those other universes.