Joe is a 12-year-old boy who loves baseball and collecting sports cards, though he struggles with playing the game itself. He is highly self-conscious about his stocky build and bowed legs. Burdened by his parents' divorce and ongoing financial struggles, he takes on odd jobs to help his mother. He discovers he possesses a physical, magical connection to baseball cards that triggers a tingling sensation and allows for time travel.

Honus is a legendary baseball shortstop for the Pittsburgh Pirates who physically travels through time after Joe holds his rare card. Known for his incredible speed and skill despite an awkward physical appearance, he grew up working in Pennsylvania coal mines. He proves to be a generous, humble figure who helps Joe overcome his insecurities about baseball and life.

Birdie is a former professional wrestler who used to play a "bad guy" in the ring and now operates a local sports card shop. He is an intimidating, greedy figure whom Joe actively dislikes. Upon recognizing the value of Joe's discovery, he immediately resorts to deceit and aggression to claim the item as his own.

Amanda is an elderly woman living alone in a dilapidated historical house next door to Joe's family. Rumored by neighborhood kids to be a witch, she is a solitary figure who relies on others to deliver her groceries. She holds onto antiques and torn photographs from her youth, inadvertently setting Joe's adventure in motion when she asks him to dispose of her old belongings.

Terry is a hardworking nurse at Hazelwood Hospital who is raising Joe on a tight budget following her divorce. She acts as Joe's primary moral guide, firmly emphasizing integrity over material wealth. She desires to protect her son but gradually learns to trust him with difficult, adult decisions.

Bill is Joe's father who lives in a nearby apartment and struggles with long-term financial instability. He originally sparked Joe's passion by gifting him his first baseball card collection. He holds a cynical view of the world, believing that capitalizing on rare financial opportunities outweighs strict ethical concerns.

Albert, nicknamed "Butts," is Honus Wagner's older brother who had a brief major league baseball career before a severe injury ended it. He is a prominent figure in the Wagner family's history, and his strong physical resemblance to both Honus and Joe leads to instances of mistaken identity.

Ty Cobb is a fiercely competitive star baseball player for the Detroit Tigers, historically known as "The Antelope" for his speed. He serves as the primary on-field rival to the Pittsburgh Pirates during the 1909 World Series, frequently attempting to intimidate his opponents with aggressive behavior and harsh insults.

Fred is a professional baseball player and teammate of Honus Wagner on the Pittsburgh Pirates. During the chaotic post-game celebrations, his boisterous and thoughtless behavior directly impacts Joe's attempts to secure a souvenir from the past.