 Karan Johar (qv) claims he was inspired to do a thriller instead  of his usual family film by Aditya Chopra (qv), who had broken  Yash Raj Films out of their romantic film mold by doing the action  film _Dhoom (2004)_ (qv). He paid tribute to Chopra by casting that  films stars, John Abraham (IV) (qv) and Esha Deol (qv).