By the 1990s, professional sports had become excessively commercialized, with marketing and endorsement deals pulling the strings. The essence of athleticism faded, overshadowed by show-boating. Stadiums transformed into advertisements, while players often sold their talents to the highest bidder. As the quality of talent dwindled, teams resorted to recruiting from prisons and mental asylums, turning sports events into chaotic brawls. Fans began to drift away even after owners attempted inter-league and inter-sport games.
In this environment, lifelong friends Joseph R. "Coop" Cooper (Trey Parker) and Douglas "Doug" Remer (Matt Stone) crash a college graduation party of a mutual acquaintance, only to be shunned for not being invited. Coop had always dreamed of becoming a sports star, but after growing up, he finds himself spending his days playing video games instead. After a few drinks outside, they challenge two classmates to a basketball game. When they realize their opponents are quite good, they cleverly decide to play a game they made up, blending basketball and baseball while inventing the rules on the fly. This street game, which allows players to distract opponents with insults—a tactic known as "Psyche Out"—sets the stage for what becomes known as BASEketball.
After emerging victorious, they refine the rules, and Coop ingeniously constructs the first BASEketball apparatus using a La-Z-Boy chair. Their friend, Kenny "Squeak" Scolari (Dian Bachar), joins them and the sport gains massive popularity in their neighborhood over the next six months. Businessman Ted Denslow (Ernest Borgnine) takes notice and meets Coop and Remer, proposing the establishment of the National BASEketball League (NBL). He insists on several regulations to maintain the league's integrity: no city relocations, no player trades, no corporate sponsorships, and open participation for all aspiring players, stating, > "Anyone can be a sports hero." With some hesitation, Coop agrees.
Fast forward five years, and the NBL thrives with teams, avid fans, huge stadiums, and the coveted Denslow Cup. Denslow owns the Milwaukee Beers—Coop and Remer's team. However, during a critical championship game, tragedy strikes when Denslow chokes on a hot dog and dies, causing Coop to miss a crucial shot and the Beers to lose to the Dallas Felons, owned by Baxter Cain (Robert Vaughn).
Denslow's will names Coop as the temporary owner of the Beers under the condition that they win the next Denslow Cup, or ownership would shift to Denslow's widow, Yvette (Jenny McCarthy). Soon, Coop and Remer meet Jenna Reed (Yasmine Bleeth), the head of the Dream Come True Foundation, and a passionate young fan named Joey (Trevor Einhorn). As Coop develops a romantic connection with Jenna, Baxter Cain aims to dismantle Denslow's rules restricting commercialization of the sport, but Coop stands firm against any modifications.
As Coop and Remer continue their winning streak, Cain enlists Yvette to try and undermine the Beers, pushing against the integrity of the league. Meanwhile, Remer agrees to endorse a clothing line to help Jenna's foundation, but this leads to complications and a growing rift between the friends. When Cain resorts to blackmail, threatening to expose a scandal involving child labor, the tension escalates, resulting in the breakdown of Coop and Remer's friendship.
With the championship game looming and their relationship in tatters, Coop embarks on a journey to Calcutta to address the child labor issue. He returns just in time for the championship, where Squeak delivers an impassioned speech that reignites Coop and Remer's collaborative spirit. They reconcile, Yvette realigns her loyalties, and despite a setback when Coop's La-Z-Boy fails, he finds renewed confidence thanks to Joey’s encouragement with a makeshift BASEketball.
After an intense match, they manage to clinch victory in the championship, allowing Coop and Jenna to reconcile. The celebration culminates with Coop and Remer joyfully skating around the stadium with their hard-won trophy, marking a triumphant return to friendship and sportsmanship.
