During the scripting stage, Hirani wanted Anil Kapoor to play the lead role. However, Shah Rukh Khan was later cast as Munna along with Sanjay Dutt as Zaheer but due to his back problems Khan was forced to turn down the film. Nevertheless, the end credits of the film thank Khan for his inputs into the script. Hirani also narrated the script to Aishwarya Rai during the time he was in talks with Shahrukh Khan. Khan and Rai were working together on Devdas at the time. Vivek Oberoi was considered for the role but in the end Sanjay Dutt took the role as Munna, which ultimately gave him an image make over and helped change the public perception of the controversial superstar; his real-life father Sunil Dutt returned to film after 10 years to play Munna's father. This is the first and only film in which real-life father and son Sunil and Sanjay appear together, although they both appeared in "Reshma Aur Shera" (1971), "Rocky" (1981) and "Kshatriya" (1993) but not in any scenes together.