Diana is a young fox girl who lives with her affluent family in a large mansion on a hill in Maple Town. She is the eight-year-old daughter of Frederick and Florence Fox, known in some versions as Hans and Chirine, and the sister of Freddy Fox, also known as Carl. Her family is considered the wealthiest in the town, a fact that significantly shapes her identity and her initial interactions with others.

Physically, Diana is an orange and light yellow fox with a brown nose and a bushy tail that has a light yellow tip. Her typical attire consists of a blue and white dress with a yellow ribbon on its capelet and a darker blue stripe on the lower half, paired with white buckled shoes. In colder weather, she adds a scarf and leggings. However, her wardrobe was notably different in her first appearance, where she wore a light blue hair bow, a yellow capelet, a blue dress with pink flowers and a pink ribbon, a pearl necklace, and light blue shoes.

Personality is the most defining aspect of Diana's character. She is often portrayed as a typical 'arrogant young lady,' prone to being bossy, stubborn, fussy, and selfish. This behavior is inherited from her mother, and she frequently acts as if she is superior to everyone else. In her early days at school, she tries to bully Patty, the new rabbit student. For instance, she once framed Patty by throwing her own necklace and claiming it was stolen. She later confessed she had lied about the necklace being a diamond because it allowed her to walk to school with a boy named Johnny every day.

Despite her snooty and domineering exterior, Diana is not without redeeming qualities. She is shown to have a good heart and is capable of recognizing when she has done wrong. An important part of her character is her ability to honestly apologize after her schemes backfire or she realizes her mistakes. Her motivations often stem from a desire for attention and validation, particularly from her busy parents. In one episode, feeling neglected because her parents were too occupied with work to praise her drawing, she tore up the picture and acted out, only to be kidnapped by the town antagonist, Gretel. After being rescued by her father, her belief in her connection with her parents was restored.

Throughout the story, Diana serves as both a rival and a friend to Patty Rabbit. Their relationship is central to her role, as her interactions with the kinder, more straightforward Patty often lead to her personal growth. She is also part of the main group of children, alongside Bobby Bear and Johnny, and participates in their adventures and hijinks. Her key relationships include her competitive dynamic with a girl named Julieta and her clear, though sometimes haughty, interest in Johnny.

Diana shows considerable development over the course of the series. While she begins as a typical antagonist to the protagonist, her character softens as she is influenced by her friends. She learns to value friendship over status, as seen when she convinces her mother not to burn an old piano she and her friends had come to love, appealing to her mother's empathy by asking if she cared about the other children. She also demonstrates genuine care for her family, such as when her father fell into debt and she tried to find a way to help him, even breaking down in tears when he expressed his gratitude. She also participates in group efforts to help others, such as when she and her friends helped clean an old castle or searched for a friend who had run away from home. Diana does not possess any special abilities; she is a normal child whose influence comes from her family's wealth and her strong-willed personality.