Casey is the star player and bruising hulk for the Mudville nine minor league baseball team. He possesses immense physical power and a preening, almost god-like confidence at the plate. Reveling in the adoration of the home crowd, he carries himself with haughty grandeur as he steps up to bat during a crucial, high-pressure moment.

The Umpire is the official adjudicating the baseball game in Mudville. He represents objective authority and the strict rules of the game, maintaining his composure despite the immense pressure of the hometown crowd. His unflinching calls quickly turn the anxious spectators into a hostile mob.

The Pitcher is the unnamed opposing player tasked with throwing the ball to Mudville's star batter. He appears physically anxious and intimidated by the massive hitter, writhing on the mound as he readies his delivery.

Flynn is a player for the Mudville nine who precedes Casey in the batting order. Widely considered a jinx by the local spectators, he possesses a poor reputation for hitting and base running but attempts to keep the game alive in the final inning.

Jimmy Blake is a widely disliked player for the Mudville team who bats directly before Casey. Often dismissed by the crowd as a fake, he faces exceedingly low expectations as he attempts to get on base.

Cooney is a batter for the Mudville nine who opens the critical final inning. He fails to reach first base, setting a grim tone for the team's last chance at a comeback.

Barrows is a player for the Mudville team who bats second in the critical final inning. Following his predecessor's lead, he also fails to get a hit, pushing the home team to the brink of defeat.

The Mudville Fans exist as a collective character representing the five thousand spectators attending the local baseball game. They are intensely fickle, swinging rapidly from deep despair to lusty cheers depending on the action on the field. They view the sport with hyper-emotional fanaticism rather than steady loyalty.