Ajay Devgun was the original choice to play one of the main characters, but he was unavailable due to his other commitments, so the role was offered to Saif Ali Khan.
Whilst shooting in the heat, the cast/crew member used to bring an umbrella over Amitabh Bachchan. He would move away from the shade of the umbrella, and when he was asked why he didn't want to come under the shade from the blistering heat, Bachchan replied he didn't want to get used to such things whilst working.
Saif Ali Khan found his lines challenging as he isn't very fluent speaking pure Hindi, and hasn't done any roles in the past that have had to mouth such dialogs.
The music score was done by Hollywood technicians in New York.
The movie landed in controversy before it released, the Dalilts (a lower Hindu caste) had found some of the dialog offensive and had protested to either remove these dialogs or they would stop the film from releasing. Prakash Jha took his stand and defended that the film has no intention to offend any caste, and subsequently got the film released with some changes to the script.