 Farhan Akhtar originally wrote the movie by casting Akshaye Khanna  as Akash, Hrithik Roshan as Siddhart and Saif Ali Khan as Sameer.  When Hrithik Roshan turn down the movie the role went to Abhishek  Bachan. After Abhisheks withdrawal Farahn take Aamir Khan with a  quick change in the previous cast, swapping Akshay Khanna as  Siddhart and Aamir khan as Akash.