The movie opens with Bobby Bowfinger sitting alone in his office reading a script. As he finishes reading the script, he gets a twinkle in his eye, believing that he's found the perfect movie moment. The next day he gathers his staff and actors and tells them about the brilliant script called "Chubby Rain" that was written by his very own accountant Afrim. They then figure that this is their only shot at making a movie. So Bobby gets out his life savings - some $2200, and they start getting the equipment and the crew that they need to make the movie. Bobby then goes to meet executive agent Jerry Renfro at a chic Hollywood restaurant. He slips the maitre d' $20 and asks to be seated at the table next to Renfro.
As he pretends to be an elite movie producer and fakes his way into having a conversation with Renfro about the script for Chubby Rain. He hands the script to Renfro and he reads through it, eventually agreeing with Bobby about the script's final moment which has the hero screaming "Gotcha suckers!!" that that is a great catch phrase. Bobby tells Jerry about the plans to get Kit Ramsey in the film's lead role. He then agrees that if Bobby gets Kit Ramsey, they've got a go picture. In Kit's mansion, he is unloading at his agent, telling him about how there's no good Hollywood moments and no good catchphrases anymore, that it's all style and no substance. The agent tries to tell him that the script he's just read is good and this movie has that moment, but it's not the moment that Kit is looking for. Kit then heads to his weekly appointment at Mindhead, a psychological collective that has obtained cult-like status among the Hollywood elite. Bobby has managed to sneak past the gate and heads to talk to Kit, now pretending to be a script delivery guy for a major Hollywood agent.
He and Kit are having what appears to be a civilized conversation, and Bobby tells about how he's about to go for his appointment at Mindhead. Kit offers Bobby a ride to Mindhead, but when Bobby reveals who he really is, Kit goes ballistic and has him thrown out of the car. Back at the office, Bobby comes up with another idea - they film the movie without Kit knowing that he's going to be in it. His producer Dave thinks this is a bad idea but Bowfinger decides to pursue it anyway. We then see a young woman named Daisy, who is looking for work, getting off a bus. She goes to Bowfinger's "studio" where he has her audition for the female part in the movie. Daisy is a naive Midwestern woman who is a first time actress seeking fame and fortune. Kit goes to his meeting to meet Terry Stricter, who is the head psychiatrist at Mindhead for his weekly meeting.
Kit talks to Terry about how he's better when he goes to his happy place and that he heavily believes in aliens and conspiracy theories. Dr. Stricter then reassures Kit that he will not do the one unforgivable action - show "it" (meaning his male organ) to the Lakers cheerleaders. Back at Bowfinger Films, Bobby is giving a pep talk to his staff about how this is the opportunity that they've been given to finally make a motion picture. And that once they're famous and successful, that Fedex truck will be making multiple stops at their studio with future projects, and that will be the day that they truly know they've made it. Bobby then wonders what exactly they're really in for with no star. Day 1: Bowfinger tells Dave to supply the equipment. He does so by checking out a camera from his day job at Universal, and using the van with S&Y Construction painted on the side.
The first shot of "Chubby Rain" is Daisy chasing Kit's limo as it leaves his mansion for Mindhead. Kit has no idea what's going on as he looks out his window and sees the action behind him. Back at Bowfinger films, they are reviewing the first shot of the movie and Bowfinger realizes that this movie is going to work. Day 2: Kit and his agent are having a meeting at another chic Hollywood restaurant. Bowfinger and his crew are going to be there.
Bowfinger cleverly disguises his crew to look like homeless people as they shoot the first scene of dialogue involving Carol and Kit. But Kit still has no idea what's going on, and Carol's approach and the dialogue about the movie - which discusses alien love, has made him even more paranoid than normal. Kit is resuming the conversation that he had with his agent about how there are no good scripts out there. Kit then heads to an emergency meeting with Terry Stricter. Kit then reveals to Dr. Stricter about his plans to show "it" to the Laker cheerleaders.
Day 3: Daisy and Slater are discussing that they both need some more scenes with Kit, and are discussing the best course of action to take as far as getting some actual screen time with Kit. Although no one still has any clue as to the fact that Kit doesn't know that he's in the movie. Afrim even has written some extra scenes with Kit to incorporate into the movie. Day 4: Dave has tracked Kit to Mindhead. In the parking lot, they film the climactic scene in the movie where Carol confronts Kit in the parking lot. Kit, still unaware of his involvement in the film, thinks that someone is actually following him through the parking lot and begins to freak out. It's then revealed that Bowfinger has his dog wearing a pair of high heels following Kit through the parking lot. Back at the offices, they review the film and Carol is completely in awe of Kit's professionalism.
Afrim is bragging about his screenwriting abilities to Daisy, who then sees an opportunity to get some more screen time in the film. Day 5: Kit is heading to an upscale department store to buy some new clothes. The store offers him the clothes for nothing if Kit makes an appearance outside their store. Kit demands $1000. Carol decides to confront Kit and then begins to talk about their screen time in the film. That makes Kit even more paranoid than usual.
At Kit's mansion, Terry Stricter makes a house call and Kit talks about how the aliens might be following him. Dr. Stricter then offers to let Kit stay in Mindhead's special "celebrity quarters". Back at Bowfinger films, they're wondering what to do now that Kit's out of the picture. Bowfinger then instructs Dave to hold auditions to find anyone that even remotely looks like Kit to get the shots for the scenes that they need.
He then settles on a guy named Jiff. Day 6: Bowfinger's first day of shooting with Jiff. who bears an unbelievably striking resemblance to Kit, has him running across US-101 in Los Angeles. Jiff fears for his life running across the freeway but Bowfinger assures him that the stunt isn't for nothing. Day 7: Bowfinger is realizing his cash supply is dwindling at an extremely rapid rate. Thankfully he has a date with Daisy that night, who's manipulating Bowfinger into getting some more screen time and time with Jiff / Kit.
Bowfinger then catches a break when Daisy leaves her wallet unguarded and then takes advantage of her "lost" credit card and uses it to purchase tons of equipment that they then use to shoot additional scenes with. Day 8: The new equipment that Bowfinger purchased allows them to shoot some indoor scenes for the movie, and Daisy and Jiff have their on screen romantic moment together. Day 9: Just as no one knows where Kit is, Carol stumbles upon an opportunity to shoot the next scene for the film - Kit is appearing at the department store that he was in just days before. They borrow Renfro's one of a kind 1946 Buick to use to shoot the scenes with. This scene they approach Kit (or Keith Kincade) in the department store, once again freaking him out.
Bowfinger is approached by a cop who stops him and asks for a film permit. Bobby instead offers him a part in the movie. As the scene unfolds, it freaks Kit out to the point where he does anything he can to run from what's happening. Day 10: While sitting at a diner eating breakfast, Jiff reveals that he's in fact the biological brother of Kit Ramsey - not just some guy who really looks like Kit Ramsey. This causes Bowfinger to have a change of heart as to how Jiff is being used in the film. But Jiff really likes working for Bowfinger and is excited to be a part of cinema where before he was working at a fast food restaurant.
Day 11: A security guard discovers the "found footage" of Chubby Rain locked up with all the rest of the equipment that Dave was borrowing and reports it to Mindhead, causing Terry Stricter to become suspicious about what's really going on. Meanwhile, they're getting ready to shoot the film's big ending scene at the Griffith Observatory. Dave checks out a crane truck and then they disguise it to shoot Kit's car from overhead. The final scene begins to play out and Kit is heading to the Griffith Observatory as originally planned. Afrim disguises himself as a mutated alien causing Kit to really freak out and get in the car, Daisy follows, and then Slater follows with Jerry Renfro's car. Just as Kit is about to say the film's signature catch line "Gotcha Suckers", Bowfinger is discovered by Terry Stricter who was proven right about how the paranoid some times are actually being followed. Back at Bowfinger Films, the group is completely defeated and begins to wonder how they're going to turn their careers around - if they have a shot at all. That is until Dave comes back with the crew and tells Bobby about how they followed Kit around to obtain some extra shots for the movie.
The footage proves to be useless until one piece catches Bobby's eye. They now have the permission they need. Bobby heads to Mindhead to show Stricter the footage they recorded of Kit. It turns out that he did in fact show "it" to the Laker Cheerleaders - only to be met with hysterical laughter. Bowfinger tells Stricter that they could use this and it'd make a great ending for Chubby Rain, but it would also ruin Kit's career. Stricter confers with his council and agrees.
We are then shown the premiere of Chubby Rain. Bowfinger gets a front row seat and is stunned to watch his vision become a reality. Back at the offices, he's greeted with a standing ovation. Then - just as he predicted - the Fedex truck shows up at his door and hands Bobby an envelope. What's inside is a contract for Bowfinger films to make a Kung Fu movie in Thailand starring Jiff Ramsey. The movie ends with the opening of the newest film from Bowfinger Productions called "Fake Purse Ninjas".