Bol Bachchan is an upcoming Indian comedy film directed by Rohit Shetty, and with a starcast including Ajay Devgn, Kareena Kapoor and Abhishek Bachchan. The is produced by Ajay Devgn was initially slated to release on Diwali 2011,, but when the director found Shah Rukh Khans Ra.One is also scheduled for the day, he postponed his film to a later date. Shetty is set to work with Khan on the Angoor remake in 2012.
The film began its initial schedule on November 9, 2010 and the filming will continue through India, New Zealand and Russia. The film is set to release on Diwali 2011.
Director, Rohit Shetty who previously director comedy flick, Golmaal 3 , did first give Ajay Devgn an offer for Golmaal 4, but Devgan said "GOLMAAL 4 will happen next to next year. Its necessary to have two years gap between two GOLMAAL films. Its not good if it comes every year.", and without Ajay Devgn the film could not go on, so Shetty delayed Golmaal 4, and announced to make Bol Bachchan also starring 41-year old Ajay Devgn.
In January 2011, it was revealed that film is a tribute to the original Gol Maal  directed by Hrishikesh Mukherjee with Abhishek Bachchan playing the role of Ram Prasad, essayed by Amol Palekar in the original and Ajay Degn playing the role of Bhawani Shankar [Utpal Dutt], who is father of filmss female lead character, Urmila, to be played by Kareena Kapoor.
On Jubilee Comedy Circus Krushna Abhishek did a performance of Rohit Shetty never giving him a film role to do, Rohit was so impressed by the performance he decided to give Krushna a role in Bol Bachchan
golmal4 will be very hit
Source : Bol Bachchan Wiki Page