A small spoiler from last night's Heroes finale, strictly about the pseudo-Mystique character.
When Nikki knocked her unconscious, the shape-shifter (who is really an illusionist instead or as well; not sure which) seemed to return to the form of the actress who regularly plays her, is that right? If so, then either she was lying when she told Micah she was "huge," or she has severe body-image problems. This second, if consciously handled, could be interestingly explored through a shape-shifter. For one thing, is she simply like someone who had dyed her hair so many times she cannot remember what her natural color is? Is this character perhaps laboring under a physical self-image a decade or more old, that no longer corresponds to her reality? Or has she perhaps even lost the ability to return to, or even just recognize, her natural state? Just some thoughts.