Director R Balki and megastar Amitabh Bachchan’s third outing Shamitabh turned out to be a box office disaster, but they are all set to collaborate a fourth time for yet another clutter-breaking film. The megastar said that working with the filmmaker is enjoyable because he offers roles that challenge him. The duo has earlier worked together in films like Cheeni Kum and Paa. Big B graciously accepted the failure of Shamitabh. “Shamitabh has been as challenging as Paa or any other (film) that I have worked in. And working with Balki is a joy, simply because he keeps challenging me with roles that I may never have done before,” said the 72-year-old. The Big B is grateful to social media sites for constant feedback on his films and performances. “Twitter followers have been large and I am most grateful to those that contribute to the platform. It has given me an opportunity to express myself to the others and to take back their expressions. It has been most rewarding,” said Mr Bachchan.