The plot revolves around the lives of Tom Yeo (杨学谦 Yáng Xuéqiān; Shawn Lee), his younger brother Jerry (杨学强, Yáng Xuéqiáng; Ashley Leong) and their friend Lim Chengcai (林成才 Lín Chéngcái; Joshua Ang). 15-year-old Tom is technologically inclined and a talented blogger, while 8-year-old Jerry enjoys the performing arts and has the lead role in his school concert. Mr. and Mrs. Yeo's (Jack Neo and Xiang Yun) busy schedules give them little time to spend with their children, leading to a strained relationship. With his mother absent, Chengcai was raised by his ex-convict father (Huang Yiliang), whose fighting skills he inherited.
During a school check for mobile phones, Tom is caught with a pornographic VCD. As his teacher confiscates it, Chengcai makes a cheeky remark that provokes the teacher into slapping him, leading to an exchange that escalates into a massive scuffle. The principal decides to expel Chengcai, while Tom receives a public caning for his part in the scuffle. Tom and Chengcai later join a local street gang; as their initiation, they are forced to shoplift an iPod. However, they are caught by two conmen with connections to the street gang posing as police detectives, who demand that they pay the fine $2000 within two days or be arrested.
While tutoring his sons, Mr. Yeo tells them that people will pay $500 for an hour of his time. Jerry, who wants his parents to come to his school concert, starts saving money, but he can't save enough and eventually resorts to stealing. After he is caught, his furious father repeatedly canes him and shouts at him, but forgives him when the boy explains that he wanted $500 to "buy" an hour of his father's time. This prompts Mr. and Mrs. Yeo to read Tom's blog and realise how unappreciated and alienated their children feel. Having finally understanding their children, the Yeo parents watch Jerry's concert, much to his delight.
Unable to raise $2000 themselves, Tom and Chengcai rob an old lady of her necklace, but regret their action and try to return it to her. A struggle occurs, and Chengcai bumps into several gangsters, while Tom's mobile phone falls out of his pocket as he is tackled by vicious vigilantes. The phone hits the ground, accidentally calling Mr. Yeo, who is doing a presentation about 3G phones for a contract worth $3 million. He rushes off to the scene and pleads the old lady to give Tom a second chance. When the police arrive, she tells them she made a prank call, which meant to give Tom another chance. Two days later, Mr. Yeo meets the conmen and gives them thousands of dollars of hell money; the conmen are then arrested by real police officers who have been waiting in ambush close by, and then Mr.Yeo heard the news of the big succeed with his company, which Tom and Mr.Yeo remain overjoyed.
Later, the gangsters whom Chengcai bumped into earlier beat him up. Mr. Lim, who happens to be nearby, tries to protect his son, but suffers head trauma after being pushed down the stairs. He is taken to a hospital, critically injured. On his deathbed, Mr. Lim tells Chengcai that he loves him and that he should pursue his talent for fighting and then die. Witnessing this scene, the principal is touched and allows Chengcai to return to school. The boy eventually becomes an internationally recognised martial artist.
After the release of I Not Stupid, a sequel was suggested, but Neo had difficulty finding a suitable topic. His inspiration was a book on appreciation education, a method of teaching developed by Chinese educator Zhou Hong. Through the movie, Neo hoped to capture the culture of Singapore at the turn of the millennium, and to explore the issue of poor parent-child communication.
Neo and Rebecca Leow co-wrote the script, which was completed in May 2005. I Not Stupid Too was produced by MediaCorp Raintree Pictures on a budget of S$1.5 million. Shanghai Film Studio had agreed to co-produce I Not Stupid Too with Raintree Pictures, but backed out because they found the film too liberal. The production crew included Daniel Yun as executive producer, Chan Pui Yin and Seah Saw Yan as producers, Ardy Lam as cinematographer and Mo Ju Li as sound editor. Besides writing and directing, Neo starred as Mr. Yeo and composed the theme song, which was sung by Hong Junyang.
Filming took place at Saint Hilda's Primary School, Presbyterian High School and other locations during the school holidays in June. Neo hired real gangsters to act in several gangster scenes as he was dissatisfied with the extras. According to him, communicating with the gangsters was difficult, but when he decided to apply the lessons from the movie and praised them for a good take, they reacted well. Several members of the cast also said that I Not Stupid Too inspired them to communicate better with their family members. On 26 January 2006, distributor United International Pictures released I Not Stupid Too on 36 screens in Singapore.
With earnings of over S$1.41 million in the first six days, I Not Stupid Too achieved the biggest opening for a Singaporean film. The movie rose to the top of the local box office, beating Jet Li's Fearless. In total, I Not Stupid Too grossed over S$4 million, becoming Singapore’s second-highest grossing movie after Money No Enough. The film was then released in Malaysia, where it made RM1.1 million, and Hong Kong, taking in HK$3.1 million. Following the success of the two I Not Stupid films, Neo has announced plans to make more sequels, as well as a remake set in China.
I Not Stupid Too was well received when it was showcased at the Cannes Film Festival. It was also one of six Singaporean movies screened at the Singapore Season film festival in China. At the 2006 Moscow International Film Festival for Children and Youth, I Not Stupid Too captured the Children's Jury Award. The film was also nominated for Best Asian Film at the Hong Kong Film Awards, but lost to Riding Alone for Thousands of Miles.
Critics praised I Not Stupid Too for its touching portrayal of the problems faced by Singaporean teenagers. According to a review in the South China Morning Post, the movie "presents a candid portrait of Singaporean society at odds with its stereotypically squeaky clean image". Nie Peng of Shenzhen Daily felt the film "captured the emotional depth and effectively conveyed the underlying theme of generation gaps", while movieXclusive.com reviewer Jolene Tan called it "a good local movie that will have [viewers] laughing in stitches and crying at certain points". However, I Not Stupid Too was also panned for being overly preachy: a reviewer for The Hindu said that the movie "feels like a public service program written by Singapore's social welfare department". Geoffrey Eu, a reviewer for The Business Times, commented that it "takes the line that the viewer needs to be clubbed into submission rather than persuaded via a more subtle line of reasoning".
A Malay language remake titled Aku Tak Bodoh (the translation of the title of the first film) was made as a Malaysian co-production between Grand Brilliance J Team Productions AMC Sdn Bhd RAM Entertainment And PMP Entertainment with Jack Neo as the executive producer and directed by his protege Boris Boo. According to Neo himself, there was already a demand to adapt the first film itself into Malay after people requested for a dubbed version of it, but it took 4 years for the plan to come into fruition. The film, starring Jalaluddin Hassan and Adibah Noor among others, was released on 14 April 2011 in Singaporean cinemas.