Though in the film the cellphone proves to be a tool for Bob Biswas as his prospective victim's photo is sent to him via MMS, in real life Saswata Chatterjee (who portrayed Bob Biswas )doesn't even use a mobile and has only a landline number as a point of contact.
Sujoy Ghosh built Khan as a character with lean physical build but full of mental strength, loyalty and patriotism. Khan smokes a relatively cheap brand of cigarette (Gold Flake) despite his high official post; Nawazuddin Siddiqui had smoked that brand of cigarette throughout his struggling days.
Saswata Chatterjee (Bob Biswas) used to play the character of "Topshe" in the Bengali TV adaptations of the "Feluda" until 2001. Parambrata Chatterjee (who plays Inspector Satyaki Sinha/Rana) replaced him on 2003 and since then he plays the role in four Bengali movie adaptations.