Kitkat, one of many costumed characters that provide a complex support structure within the heroic history of Astro City. To date however, she has mainly been stage-dressing, one of the many super-hero "spear-carriers" used to decorate and enhance the current narrative of a given story arc. Her ongoing and consistent appearances suggests a well formed outline of the character's own history. How much of that detail will be revealed, or if there is a possible future tale dedicated to her viewpoint... ah there's the rub, and the teasing fun associated with the enormous legion of minor characters that make their brief appearances in Astro City tales.
The exact nature of her relationship with Leopardman has not been revealed. Nor has much of anything else about this mysterious background character.