Owen is the athletic fraternal twin brother of Russell. He excels at basketball and views the sport as a core part of his identity. Lean and built for physical activity, he relies on his athletic status for social standing and feels protective of his domain when his non-athletic twin is forced to try out for the team.

Russell is Owen's fraternal twin, characterized by his tall, skinny build and academic focus. As the leader of the Masters of the Mind club, he prefers creative problem-solving and mathematics over physical sports. He is initially reluctant and confused when a coach orders him to try out for the basketball team simply because of his height.

Arthur is a wealthy middle school student with his sights firmly fixed on attending Harvard University. He frequently wears apparel bearing the college's name and uses extracurricular activities strictly to build his academic resume. He views his peers as stepping stones for his own future success rather than actual teammates.

Coach Baxter is the new middle school basketball coach and gym teacher. He runs intense scrimmages and disrupts the status quo by implementing strict, open tryouts for all students. Recognizing a physical advantage in the hallway, he decisively orders the non-athletic Russell to try out, initiating the central conflict of the story.

Mr. Evans is Owen and Russell's father and a former college basketball player. He strongly values sports as an important part of childhood development. He enthusiastically supports Russell's forced entry into basketball tryouts by outfitting him with proper gear, hoping it will help him experience a different side of growing up.

Mrs. Evans is Owen and Russell's mother. She is protective of her children's current interests and questions the necessity of forcing Russell into physical sports when he is already happy and successful in his academic pursuits.