Raju Hirani came to him with two scripts , 3 Idiots and Munna Bhai. He has always said more than the script , it's how comfortable he feels with the director that matters a lot to him. He even said something on those lines in the recent interview he has done. He was in talks with Imtiaz and Anand for I think almost more than a year , so after reading the script , he just kept spending more and more time with them to build up a rapport and to discuss the movie as well. Everyone works differently I guess. Not that Raju Hirani is a bad person or anything. I think he's a fantastic director and always comes across as extremely polite and sweet but I'm guessing something must have not worked out when it came to those movies.