This was Sunil Dutt's first film appearance in 10 years.

Casting for the lead role went through several process. First it was given to Shah Rukh Khan, but he declined due to his neck injury, then it was offered to Vivek Oberoi. Finally the producers casted Jimmy Shergill for the part, but they later interchanged his role with Sanjay Dutt who was cast as the patient 'Zaheer'.

Nawazuddin Siddiqui who was a struggling actor back then plays the role of a pickpocket who robs Sunil Dutt's purse at the station.

This being Rajkumar Hirani's directorial debut, he wanted everything to be authentic. For the dissection room scenes, he considered shooting in a real dissection room, using real dead bodies. With due respect for everyone's feelings, the scene was shot on a set with a real person doubling up as a cadaver.

Rani Mukerji was very keen on this film and had signed on for the role of Chinky, but she couldn't do the film due to date problems. Then Tabu was brought in, but she soon dropped out. Finally, the role went to Gracy Singh.

Rajkumar Hirani was afraid on how doctors would treat him after watching the film since he made so many jabs and jokes at Indian doctors.

There are several pigeons in the film. This is a reference to the classic gangster film Parinda (1989), which was directed by Vidhu Vinod Chopra.

Sunil Dutt played father to Sanjay Dutt in Rocky 1981 and Kshatriya 1993 but this was the first and last time they both shared screen space together

The semicircular hall had 15-feet windows, which had to be broken open for the lighting to be right.

Last film of Sunil Dutt.

The original choice for Circuit was Makrand Deshpande.

Dr. Asthana is a professor of anatomy but also performs surgeries in the movie. In reality it's only surgeons who perform surgeries. Anatomy Professors perform dissections of cadavers.

Arshad Warsi won the Filmfare and Zee cine best comedian award in 2004.

In the scene where the senior students are making the junior students dance naked, the song in the background is "Ishq Samundar" from the movie Kaante (2002) which also stars Sanjay Dutt.

Sanjay Dutt reduced his weight for the role.

Sanjay Dutt and Arshad Warsi's pairing worked and they both were paired together in many films.

Rohini Hattangadi who plays Sanjay Dutt's mother is older to him by a few years.

Considered the turning point for Arshad Warsi who had been rejected by Bollywood and failing to secure many offers prior to this film.

Loosely based on the 1998 movie Patch Adams, starring Robin Williams.

Sajid Khan was the first choice for the role of Circuit before Arshad Warsi got it. Also Vivek Oberoi,Anil Kapoor and Shahrukh Khan were all approached to play Munnabhai which was eventually played by Sanjay Dutt.