Tommy Bangs is a mischievous student at Plumfield boarding school run by Jo and Fritz Bhaer. He keeps chickens and agrees to let fellow student Nat Blake keep one egg from every dozen found, aiding Nat's plan to save earnings for a violin. His prankster nature initially shows as bullying toward new student Nan Harding, though peers tease him about developing a soft spot for her.

He shares a rambunctious and outspoken personality with Nan, creating a "Birds of a Feather" dynamic, and carries a persistent crush on her despite her consistent rejection of his romantic advances. This unrequited affection continues into young adulthood, where he enrolls in medical school primarily to pursue Nan, despite lacking genuine interest in the field.

His loyalty emerges when Nat is falsely accused of theft; Tommy participates in the initial suspicion but later supports Nat during the ordeal. He also launches "Tommy Bang's Company," showcasing his business inclinations.

During young adulthood, Tommy becomes accidentally engaged to a girl named Dora. While initially considered an "Accidental Proposal," he finds genuine contentment in this relationship, leading him to abandon medical studies. He subsequently joins his family's business, recognizing it as a better fit for his skills and temperament.

The anime adaptation concludes Tommy's storyline with him leaving Plumfield to attend school in Boston, distinct from the book narrative. His journey illustrates a transition from a playful, sometimes insensitive boy to a settled adult who finds personal and vocational fulfillment through pragmatic self-awareness rather than idealized pursuits.