Bobby Bowfinger, an ambitious B-movie producer, has been dreaming of directing a film since he was just ten years old. Now, with a meager $2,184 saved up for production, he is eager to turn his vision into reality. He has a script titled "Chubby Rain" written by an accountant named Afrim and a dedicated camera operator, Dave, who has the advantage of using studio equipment through his gig as a gofer. To complete his project, Bowfinger gathers a cast of eager actors and a crew composed of undocumented Mexican immigrants, all while desperate for a studio deal to distribute his cinematic masterpiece.
Bowfinger secures a commitment from high-ranking Universal Pictures executive Jerry Renfro, who agrees to distribute the film, provided that it includes the current action superstar, Kit Ramsey. However, Ramsey, known for his pompous, neurotic, and paranoid demeanor, initially refuses to participate. In a clever twist, Bowfinger devises a scheme to stealthily film Ramsey's scenes without his awareness. The actors are briefed to recite their lines in public, insisting that Ramsey is method acting and will not engage outside of their scenes, capturing his bewildered reactions with hidden cameras.
The operation appears to be effective, especially when Ramsey, who is entangled with a Scientology-like group named MindHead, begins to believe in the film's alien invasion theme. This delusion results in a remarkably authentic yet intense performance. Unfortunately, as the pressure mounts, Ramsey retreats to protect his frail mental state, causing production delays.
In a bid to keep the project alive, Bowfinger hires a lookalike named Jiff. Jiff, who is unsuspecting and cheerful, becomes an unwitting participant in the chaotic plan; Bowfinger even convinces him to dash across a busy freeway under the pretense that the vehicles are being piloted by "stunt drivers." During interactions with the rest of the cast, Jiff casually reveals that he is actually Kit's twin brother, providing crucial insight for Bowfinger to locate and ambush the elusive star to film the grand finale.
With only one pivotal scene left to shoot at the iconic Griffith Observatory, Bowfinger is particularly focused on Kit's climactic line, "Gotcha, suckas!" Wanting to keep the film's momentum, he instructs Daisy, the female lead, to help Kit navigate through the scene while feigning to offer strategies for dealing with "aliens." When filming begins, however, Kit falls into a panic, struggling to deliver the critical line. As tension mounts, Kit's MindHead mentor, Terry Stricter, steps in after uncovering that Kit's "aliens" might not be mere figments of his imagination, bringing production to a standstill.
In a twist of fate, Bowfinger's crew presents him with B-roll footage they captured off-set, showcasing a comical yet embarrassing moment where Kit, with a paper bag on his head, exposes himself to the Laker Girl Cheerleading Squad, an act previously discouraged by Stricter. Armed with this incriminating footage, Bowfinger blackmails Stricter and the higher-ups at MindHead, threatening to publish the scandal and destroy Ramsey's career, which would, in turn, jeopardize MindHead's financial stability given Ramsey’s status as a significant contributor. Faced with such leverage, Stricter concedes, allowing Bowfinger to complete the film with Kit's involvement.
Finally, the film reaches its premiere, leaving the cast and crew in awe of the finished product. In the aftermath of their success, Bowfinger receives an enticing offer to direct a martial arts film in Taiwan featuring Jiff. The film concludes with an exhilarating fight scene from the upcoming movie, Fake Purse Ninjas, showcasing the talents of all who contributed to the making of Chubby Rain.
