Lady Oppenheimer is a cat who serves as the guardian and instructor for CoCO and NiCO, two young cats undergoing training to become graceful and elegant cat princesses. Her role in the story is to oversee their daily lessons, ensuring they learn proper princess behavior while also keeping them out of trouble. She is described as strict but caring, balancing discipline with genuine concern for her charges. Her personality is defined by patience and a no-nonsense attitude, yet she shows warmth when the sisters make progress. CoCO and NiCO keep her quite busy with their playful mischief and attempts to learn, which creates a dynamic where she is often the voice of authority and guidance. No detailed background or personal history is provided, and her development is limited to her steady presence as a mentor. She does not display any special abilities beyond her role as a teacher and caretaker, and her relationships are centered entirely on the two sisters she trains.