Tommy Bangs, a paying student at Plumfield boarding school unrelated to the Bhaer family, possesses a naturally mischievous, rambunctious, and happy-go-lucky personality. His frequent pranks and occasionally bratty demeanor make him a source of lighthearted amusement among the other children. Upon Nan Harding's arrival, Tommy initially teases and bullies her, reflecting his disruptive tendencies. His friends later notice he develops a soft spot for Nan, teasing him about his crush. Despite their clashes, Tommy and Nan share similarly energetic and outspoken natures, fostering an eventual camaraderie and unique bond as "birds of a feather."

Tommy demonstrates initiative by running a small business selling goods to the other children, though his naivety in financial matters is revealed. His character faces a significant moral test when a small sum of his money goes missing; he falsely accuses Nat Blake based on circumstantial evidence and Nat's history of minor dishonesty. Tommy participates in the collective shunning of Nat until the real thief is exposed. Following this, he shows remorse and reconciles with Nat, indicating capacity for growth.

Background surfaces during Thanksgiving where Tommy expresses missing his mother, adding emotional depth. While not academically inclined like Demi or artistically talented, Tommy contributes to the school's lively atmosphere through playful antics and a growing willingness to mend relationships after conflicts. His journey involves navigating minor disputes and misunderstandings, with earlier jerkish tendencies softening into a more integrated group role. Tommy departs Plumfield at the series' conclusion to attend school in Boston.