Jake is a ten-year-old fourth grader at Despres Elementary School who is recounting a story from his time in the third grade. He considers himself a normal kid who loves computer games and playing with his best friend. However, the announcement of a local science fair with a brand-new computer as the grand prize brings out a fiercely competitive side in him, threatening to turn him into the kind of aggressive student he usually despises.

Phil, mostly known as Willie, is Jake's upbeat and optimistic best friend. The two boys share a passion for computers and spend much of their free time playing video games together. Phil assumes the best in people and cheerfully offers to share the grand prize if he wins, serving as a contrast to Jake's secretive and possessive attitude regarding the science fair.

Kevin is one of the third grade's two notorious competitive students. Described as having red hair, freckles, and unblinking blue eyes, he views school as a fierce competition to prove his intelligence. He aggressively questions Jake about his science fair plans and intentionally shows off his own project on ants to intimidate other students into quitting.

Marsha is the other major academic competitor in Jake's grade. While Kevin is direct in his interrogations, Marsha employs sneakier tactics, constantly spying on Jake's activities to uncover his project topic. She is determined to win the science fair grand prize and consistently waves her hand in class to demonstrate her superiority over her peers.

Pete is a quiet student in Jake's third-grade class who genuinely loves science for its own sake. He spends his free time observing insects, studying rocks, and learning about nature. Unlike the other students competing fiercely for the grand prize, Pete views the science fair as a natural extension of his everyday hobbies.

Jim is Jake's well-meaning but overenthusiastic father. He has a history of causing minor household disasters by refusing to read instructions or ask for directions. When he learns about the science fair's grand prize, his eagerness threatens to completely overtake Jake's project.

Mrs. Drake is Jake's mother and the organized, meticulous parent in the Drake household. She keeps her husband grounded, gently teasing him about his tendency to assume he knows everything.

Abby is Jake's younger sister, a typical first grader. She looks up to her family members and innocently explains the meaning behind the teasing nicknames her mother gives to her father.

Mrs. Snavin is Jake's third-grade teacher. She facilitates the science fair process, answers her students' frantic questions about the rules, and manages the varying personalities in her classroom with patience.

Lenny Cordo is the manager of Wonky's Super Computer Store. By sponsoring Despres Elementary School's first science fair and offering top-of-the-line computers as prizes, he inadvertently kicks off a frenzy of intense competition among the students.

Mrs. Karp is the principal of Despres Elementary School. Jake humorously describes her appearance as resembling a giant piece of celery.

Mrs. Brattle is Jake's former second-grade teacher. She is remembered for her gentle attempts to rein in the highly competitive students by reminding them to give others a chance to speak.