Jackie is the central character of the story, a young female bear distinguished as the only sister among twelve bear siblings. Her physical design features notably large ears and a uniquely flattened mouth, which gives her a perpetually slightly wistful or melancholic expression that tends to evoke a sense of gentle sympathy from observers.

In terms of background and personality, Jackie is depicted as being quite childlike, a trait shared by all young children, and is not presented as an exceptionally special individual but rather as a relatable figure whom anyone might see in their own child. She is fundamentally kind, clever, and brimming with curiosity, though this is balanced by a headstrong and occasionally mischievous nature. Her creator describes her as a girl with considerable spirit who somewhat breaks the mold, a very strong-willed individual who confidently declares "I am who I am". This spirited exterior is tempered by a deep, gentle care for the people around her. She loves to eat and enjoys cooking, spending time outdoors viewing flowers, sleeping in, and dressing up in colorful dresses adorned with ribbons.

Regarding her role in the story and motivations, Jackie lives happily surrounded by her eleven older brothers, who are consistently kind and deeply concerned for her well-being, even if they are occasionally somewhat unreliable. Her primary motivation stems from her relationships and her compassionate heart. One significant event in her narrative involves meeting a young girl bear named Katie in a meadow. When Katie falls ill due to her frail constitution, Jackie is compelled to act, embarking on a grand adventure with her brothers to help her new friend recover, demonstrating her determination to care for those she loves.

Jackie's key relationships are central to the story. She shares an incredibly close bond with her eleven brothers, who cherish her as the youngest sibling. She also forms a sweet friendship with a white bear named David. Her encounter and subsequent quest to save the sickly Katie further highlight her role as a nurturing and loyal friend.

In terms of development and abilities, Jackie matures gradually through her experiences, particularly through learning to care for others and face challenges for their sake. While she possesses no explicitly supernatural or extraordinary abilities, her notable traits include her infectious curiosity, her skill in the kitchen, and above all, a compelling personal charm. She is regarded as a healing presence, possessing a magical quality that draws people to her and allows her to bring comfort to those around her simply by being herself.