The train Shekhar Rai is riding during the song "Kasto Mazza" is the same one his mother, Sharmila Tagore, was riding in the film Aradhana (1969)
At a special preview of the film Amitabh Bachchan asked to provide narration for the film, saying it reminded him of his time as a struggling actor in Calcutta.
The music that plays everytime the characters of Girish (Sanjay Dutt) and Lolita (Vidya Balan) see each other is actually a small segment taken from the song "Ek Ladki Ko Dekha" from another Vidhu Vinod Chopra film, 1942: A Love Story.
Kaisi paheli" from the movie Parineeta composed by Shantanu Moitra is definitely inspired by the Louis Armstrong classic "A kiss to build a dream on.
Vidhu Vinod Chopra was initially not too pleased with the casting of Saif Ali Khan as Shekhar thinking he was not strong enough as an actor. However, with Saif and Pradeep Sarkar's insistence, Chopra realized that he was the perfect choice.