- Directors: Rajkumar Hirani
- Producers: Vidhu Vinod Chopra
- Writers: Rajkumar Hirani, Abhijat Joshi
- Genres: Comedy, Drama, Romance
- Actors: Aamir Khan, R Madhavan, Sharman Joshi, Kareena Kapoor, Boman Irani, Omi Vaidya, Parikshit Sahni
Farhan Qureshi (R. Madhavan), is about to travel in a plane, when suddenly he receives a phone call. He fakes a heart attack, gets out of the airport, and calls his friend Raju Rastogi (Sharman Joshi), telling him that he has got a call by someone who claims that he knows where they can find their old friend Rancchoddas Shyamaldas Chanchad (Aamir Khan). However, when they reach the place, they find out that the caller was an old batch mate Chatur Ramalingam (Omi Vaidya), who was also known as “Silencer” in the college days. He reminds them of a ten year old bet between him and Rancho that who will be more successful. He tells them that he knows where Rancho is, and the three seek a journey to find him.
The movie goes in flash back, where Farhan, Raju and Rancho join the Imperial College of Engineering, a.k.a. ICE, a fictional Indian engineering institute. It is shown that Rancho is an extraordinary student, or an Idiot, as labelled by the Professor Viru Sahastrabudhhe (ViruS) (Boman Irani), due to his intense interest in machines.
Rancho becomes an important part of both his friends, as he makes Farhan realize that his passion is photography, not engineering. He also helps Raju boost his self confidence, and helps him realize that Ramalingam (Silencer) just takes in the words, does not learn it. Other things include helping ViruS’s elder daughter in her pregnancy, saving Raju’s father, making ViruS remove his mustache on a bet that Raju will get a job through campus interview, helping both his friends clear their papers and falling in love with ViruS’s younger daughter Pia (Kareena Kapoor). ViruS also gifts him his pen, marking him as his best student.
Suddenly then, Chotu reveals that he really is Phunsukh Wangdu, a scientist, who likes to teach and change the education system. Incidentally, he is the person who Ramalingam intends to find, so that he can sign a deal with him, as his job is based on that deal. Thus Chotu finally proves that he is much better than him.