For the scene when Siddharth runs towards an oncoming train, Aamir Khan preformed his own stunt. It wasn't until he saw the scene in the editing room that he realized how close he had come to being genuinely hit by the train.
Aamir for the first time sang in his voice for Aati Kya Khandala and it became a rage.
For the climax, Aamir didn't wash his face for 8 days to look suitably battered.
Deepak Tijori's role was a reference to his role in Jo Jeeta Wohi Sikandar which too starred Aamir.
Sharat Saxena's first full fledged role, he normally played second fiddle, Apparently he impressed Bhatt while working on Duplicate 1998 as a side villain. Aamir Khan also encouraged him and convinced Mahesh Bhatt.