Jimmy Livingston was born without an immune system and is forced to live in a sterilized dome in his bedroom, earning him the title "Bubble Boy" by his neighbors. Jimmy's devout, right-wing, Christian mother only exposes him to Highlights magazine and the Land of the Lost for entertainment. When he is a teenager, a girl named Chloe moves in next door. Jimmy is immediately taken with her, and eventually befriends her despite his mothers' discouragement.
One day, Chloe visits Jimmy and tells him that she is leaving for Niagara Falls to marry her boyfriend, Mark, in three days. Jimmy is upset by this revelation and they separate on bad terms. Later, Jimmy opens a gift Chloe had brought him, a homemade snow globe with the phrase I Love You written in it. Jimmy realizes that Chloe cares for him. Realizing how much he cares for her, Jimmy builds a mobile bubble suit and runs away from home, determined to stop the wedding.
On the first day of his journey, he's unable to afford a bus ride to Niagara Falls, but is picked up by an overly enthusiastic cult on a pilgrimage towards enlightenment. But after Jimmy unintentionally offends the cult (by referring to them as a cult), he is marooned in the desert. By this time, Jimmy's mother has discovered her son missing, so she and her husband set off to find Jimmy.
While traveling through the desert, Jimmy meets Slim, a biker with a flat tire. Jimmy offers to fix the flat with some patches and the two become friends. Elsewhere, Gil, the leader of the cult Jimmy met, has revealed their messiah is "the round one," and that whoever rejects him will suffer. The group who abandoned Jimmy regret their actions and set off to find him. Jimmy and Slim have traveled to Las Vegas in hopes of scoring enough money to get to Niagara Falls. However, Slim gets caught up in the Vegas life so Jimmy goes on without him. The cult runs into Slim in Vegas while asking for directions. Slim recognizes them from Jimmy's story and threatens them, only to have his bike destroyed by the cult bus. Enraged, Slim rallies a gang of bikers to get even.
While riding a motor scooter he won in Vegas, Jimmy is recognized by his parents, but veers off the road and boards a train filled with circus freaks and conducted by their "owner," Dr. Phreak. Dr. Phreak finds Jimmy and announces that he's keeping him as an attraction of his circus. Jimmy refuses, knocking him unconscious, allowing the circus freaks to escape.
Jimmy then wanders into a restaurant where an Indian man is being antagonized by the ignorant townspeople. When Jimmy tries to defend him, the townspeople begin to probe him about his suit, but panic and evacuate the restaurant when they misunderstand his illness. The sheriff locks him in the restaurant and quarantines it, unintentionally setting the building on fire. Luckily, Jimmy is saved by Pushpop, the Ice Cream & Curry truck driver he had defended earlier. He and Jimmy escape the town that now is in flames. Pushpop thanks Jimmy for his earlier kindness and agrees to take him to Niagara Falls. Meanwhile, Jimmy's parents have met up with Dr. Phreak, whom Jimmy's mother mistakes for a child and brings along with them. Elsewhere in Niagara Falls, Chloe is apprehensive about marrying Mark and can't stop thinking of Jimmy.
Later, Pushpop accidentally runs over a cow and feels he must atone for his actions, unable to continue the journey. Jimmy sets off on foot and ends up in a small town in Illinois. Here he meets Pappy, a cab driver who agrees to take him to Niagara Falls for $500 dollars. To earn the money Jimmy goes into a Japanese casino nearby and enters a mud wrestling competition with two women for a convenient prize of $500. Jimmy eventually wins, but just as he is about to leave he runs into the cult again. Proclaiming him as their chosen one, they plan on "releasing" Jimmy from his bubble. Luckily, the freaks have followed Jimmy and realizing he's in danger, disguise themselves as members of the cult and trick them into believing they're mutating for their earlier crimes against Jimmy. During this commotion, Slim and his bikers arrive on the scene. The Bikers, the Freaks, and the Cult all begin fighting to "save" Jimmy in their own ways. In the confusion, Jimmy escapes in the Taxi.
On the last day of his journey, Pappy and Jimmy have now arrived in New York, but Pappy is unresponsive, having apparently died behind the wheel overnight, forcing Jimmy to abandon the moving taxi before it crashes. Jimmy tries to call Chloe to tell her of his success, only to reach her fiancé Mark, who rudely convinces him that Chloe doesn't really love him. Jimmy becomes depressed at this assumed rejection and calls Dr. Phreak, ready to assume his role as a freak like the others. However, his parents overhear Dr. Phreak's conversation, and upon learning his location, dump Dr. Phreak out of their (moving) car and rush to retrieve him.
When his parents pick him up, Jimmy and his father are sitting alone in the car. His father (who is more level-headed than his wife) regrets that Jimmy is giving up when he is so close. Jimmy's father then looks the other way while Jimmy escapes to finish his mission. Upon his mother discovering this, they begin chasing him down in the car, but a biplane swoops down out of nowhere and picks Jimmy up. The pilot is Pappy's Brother, Pippy. Finally, Jimmy reaches Niagara Falls but falls out of the plane and into the Falls itself.
Jimmy manages to escape the water and arrives just in time to stop the wedding. He then removes his bubble suit, allowing him to touch the girl he loves for the first time. Upon kissing her, Jimmy collapses and presumably dies in front of everyone in the church, as well as all the people who have been chasing after him (the cult, the Freaks, the Bikers, and his parents.) Jimmy's mother then (encouraged by her husband) confesses that Jimmy had developed an immune system when he was four, revealing that he is not actually dead at all and Jimmy's perfectly fine, health-wise. Mrs. Livingston had hidden this fact from Jimmy to protect him from the "corrupting" world. Jimmy forgives her and resumes kissing Chloe.
Finally, Jimmy and Chloe are married with all of Jimmy's new friends in attendance. Jimmy's mom (who is revealed to be a former girlfriend of Slim nicknamed Wildfire) rides off with Slim and Jimmy's father. Pushpop has become the new leader of the former cult who are apparently now followers of Hinduism. Dr. Phreak has befriended his band of freaks. Pippy and Pappy (who've reconciled after a past disagreement), drive off with Jimmy and Chloe to their honeymoon.
Film ini bercerita tentang sebuah keluarga miskin, seorang anak bernama Siau Ti dan ayahnya yang berprofesi sebagai kuli bangunan (diperankan Stephen Chow). Walaupun miskin dan serba kekurangan, sang Ayah yang tidak sekolah selalu menekankan agar anaknya tidak suka berkelahi, tidak suka berbohong, dan selalu rajin belajar. Untuk yang terakhir itu, sang ayah bela-belain kerja banting tulang demi menyekolahkan sang anak di sekolah ternama).