Being able to draw a young girl with crazy red hair once is all fine and dandy, but to accompany her on her adventure requires me to understand how she looks from all angles. The reader needs to identify her in all situations, often, particularly in the case of Hattie wearing assorted headgear, a significant feature may be hidden. How does she move? What is expected of her as a performer? How does she express emotion? Which emotions are required? Character development is all about building a relationship with the character you're working with. Sometimes it can be easy, others, not so.