Not many know that Kareena Kapoor was a strong contender to play the role that eventually went to Kajol. But it looks like SRK's chemistry with Kajol won the battle for the heroine.
Aamir Bashir [the young cop in A Wednesday] was supposed to play Shah Rukh's younger brother but unfortunately, he was denied a visa to the United States. Jimmy Shergill then replaced him.
Likewise, Shabana Azmi was supposed to play Shah Rukh's mother in the film. But when the shooting schedule got delayed because of Shah Rukh's shoulder surgery, Azmi opted out. Zarina Wahab has replaced her.