- Finn Finnegan: The protagonist of the story. He is a curious and intelligent 7th-grade student who is looking for ways to earn extra credit in his classes.
- Caroline Parks: Finn's close friend and classmate. She is also a bright and motivated student who supports Finn in his extra credit endeavors.
- Mrs. Granger: Finn and Caroline's teacher who assigns extra credit opportunities to her students. She is a kind and encouraging educator who wants her students to learn and grow.
- Finn's parents: Finn's loving and supportive parents who are always there to help him with his schoolwork and extracurricular activities.
- Mr. Mitchell: Finn's neighbor who is a retired engineer and helps Finn with his extra credit projects. He is a wise and knowledgeable mentor who shares his expertise with Finn.