Om Shanti Om (Hindi pronunciation: [o:m Sa:ntI o:m]) is a 2007 Indian romantic melodrama film directed and co-written by Farah Khan with Mayur Puri and Mushtaq Shiekh. It stars Shah Rukh Khan as Om, a junior artist of the 1970s who has a crush on a secretly married superstar, played by Deepika Padukone. Her husband, a producer played by Arjun Rampal, kills her in a fire;

Shah Rukh was cast as the lead; he gained six packs for a song sequence. He felt Om Shanti Om was a "happy film". Farah was advised by Malaika Arora to cast Padukone as the female lead, who was suggested by Wendell Roddick, under whom Padukone was working. She was cast without a screen test. Khan felt that she was "a beautiful, classic Indian beauty" who fit the role of an actor of the 1970s. She was excited at the prospect of working with Shah Rukh and said, "I've grown up watching [Shah Rukh] and always admired him so much. To get to work with him ... is quite wonderful. It was also fantastic that Farah showed faith in my talent and cast me opposite him."  In preparation for her role, Padukone watched several films of actresses Helen and Hema Malini to study their body language. Her character was modelled after Malini and nicknamed Dreamy Girl after her the latter's nickname as Dream Girl. Rampal was approached by both Khan amd Shah Rukh at the latter's New Years Eve party. Rampal was initially reluctant to do the role as he felt it was "too evil" for someone like him. With persuasion from Shah Rukh, he agreed. Rampal wore a mustache in the film which was suggested by Shah Rukh. Shreyas Talpade played a supporting role as the best friend of Khan's character. After the release of Iqbal (2005) and completing the filming of Dor, Talpade, who attended the same gym as Khan, was called for a narration of what would be Om Shanti Om. He agreed to do the role.  Kirron Kher, Bindu and Javed Sheikh also appear in the film. 31 Bollywood film actors appeared in cameo appearances for the song "Deewangi Deewangi". Other actors were also supposed to play cameos, including Fardeen Khan, who was arrested at Dubai airport in a drug case. Dev Anand refused as he always played lead roles in his career. Dilip Kumar and Saira Banu didn't appear in the song, despite plans to include them. Amitabh Bachchan refused due to his son's wedding, while Aamir Khan refused due to Taare Zameen Par's (2007) pending editing. Khan hsd wanted the three Khans to appear together in a film. Rekha, who appears in the song, carried out 2 days of rehearsal for it. All those who appeared for the song received gifts, including a Blackberry phone and a Tag Heuer watch.Answer this question using a quote from the following article:

Were there any difficult casting decisions?
Other actors were also supposed to play cameos, including Fardeen Khan, who was arrested at Dubai airport in a drug case.