Farley Drexel "Fudge" Hatcher is Peter’s obstinate and energetic toddler brother, whose antics often cause chaos and draw the attention of their parents.

The overwhelmed mother of Peter and Fudge, she struggles to balance the demands of her energetic toddler and often relies on Peter for assistance.

Peter's father, Warren Hatcher, is a hardworking account executive in advertising, who supports the family, but often finds parenting challenging.

Peter’s best friend and classmate, he shares adventures with Peter in Central Park and helps him with school projects, showing a loyal and understanding nature.

Peter’s neighbor and classmate, often acting as a rival, who sometimes takes control during school projects but also attempts to babysit Fudge.

Peter’s small turtle, whom he cares for and regards as a personal and prized possession separate from his brother, Fudge.