The first story draft of Om Shanti Om was written by Farah Khan on Andrew Lloyd Webber's letterhead. Farah had gone to London for the Bollywood-themed musical, Bombay Dreams, in 2002 and was staying in Andrew's house. She penned down her thoughts on his letterhead. But she made Main Hoon Naa before Om Shanti Om. The complete screenplay, except for some portions was written by Farah in two weeks flat
Shahrukh Khan who plays a struggling actor in the movie in the first half apparently fights a tiger while trying to impress Deepika. He tells her that he is a rising star from the South Indian film industry and that his name is Omswami. His favourite line in the film is 'Atti Patti Katti'. The scene was canned in Bombay's Film City. Shahrukh Khan also plays a superhero "Mohabbatman" in the film and rescues Malaika Arora. Mohabbatman, like superheroes, wears his underwear over his tights! However, the super villain wears his underwear inside his tights
31 stars including Shahrukh make a special appearance in the Deewangi song including Rani Mukherjee, Preity Zinta, Rekha, Jeetendra, Ritesh Deshmukh, Aftab Shivdasani, Shabana Azmi, Kajol, Priyanka Chopra, Shilpa Shetty, Arbaaz Khan, Amrita Arora, Vidya Balan, Juhi Chawla, Saif Khan, Sanjay Dutt, Salman Khan, Mithun Chakraborty, Dharmendra, Tusshar Kapoor, Karisma Kapoor, Tabu, Urmila Matondkar, Sunil Shetty, Govinda, Bobby Deol etc. Nobody charged Shah Rukh anything for making an appearance in the Deewangi song. Everybody did the song gratis. Knowing Shah Rukh Khan, he sent each of the stars who made a special appearance in the film, a gift hamper. The gift hamper had stuff like a Tag Heur watch, a Nokia mobile phone and other items.
Farah Khan was keen on having Dev Anand in the Deewangi song, however, the actor declined the offer as he never does special appearances. Dev Anand explained that till date, he has always played lead roles and he did not wish to break his tradition by doing something like this. He therefore politely declined the offer, gave regards to Shah Rukh Khan and gave his best wishes to SRK and Farah for their film. Sridevi is another actress who refused to be a part of the song because she wanted to appear in the song with husband Boney Kapoor. But since the song had actors and actresses only and not their spouses or film producers and directors, she could not be accommodated.
Before Vishal-Shekhar stepped in to compose the music for the movie, A R Rahman was signed for the music composition. The reason why A R Rahman opted out of this film was that he wanted the music rights to stay with the Composer and the Lyricist along with the producer, something which Farah and Shah Rukh Khan didn't agree with.
Farah Khan convinced a veteran music director Pyarelal to come off his self-imposed exile from the current film music scene to compose a song for Shah Rukh Khan's Om Shanti Om. The song was created in nine shifts spread over three days. And in LP style the song's recording happened with a 150-plus orchestra, a rarity in today's age of digitally-arranged music making. 40-45 different drums ranging from tabla and dhol to duff, 40 plus violins and 22 woodwinds amongst other instruments were used for the song
Farah Khan also approached Aamir Khan to make a special appearance in the Deewangi song but he pleaded inability to shoot. He was busy with the shooting of Taare Zameen Par and his participation in the song would have delayed his film and, in turn his new film, the Ghajini remake too. Anil Kapoor also did not agree to become a part of the song. Anil feared that he would be made fun of, on the sets. Also, Anil didn?t feel like being one among so many actors!.