During a shoot, Shah Rukh Khan's wedding ring slipped off his finger. Khan had everyone on the sets searching for it, with the implausible excuse that if they didn't find it, he would have to get married again in order to get himself a new wedding ring. Needless to say, they found it quite quickly.
Hrithik Roshan was considered for the title role, but upon completing the script, Farhan Akhtar realized that a more mature actor was needed and thus Shah Rukh Khan took the role.
Apparently, the former Prime Minister of Malaysia Mahathir Mohamad, who had previously declined even Hollywood films to be filmed in the Petronas Towers, gave his permission for the crew to film inside his personal office in the Towers.[
A fight sequence between the Don and DCP DeSilva was being shot in Langkawi. Unfortunately, the fight choreographer was messing up, and Boman Irani had to leave for a flight to a shoot in Goa. So, with time running out for Irani, Shah Rukh Khan choreographed the sequence. Khan explained to Irani the scenes, when to enter the frame, etc. after several takes the sequence was finally executed and Irani caught his flight in the nick of time.
Don's disc is actually a PSP UMD.