Director Kunal Kohli sent Aamir Khan and Kajol a draft of the script, hoping they would agree with each other. His plan backfired - each of them sent back their revised versions of the script, with their own little adjustments, which included more depth and flesh to their own characters and less to the others.
Lara Dutta admit that she only accepted the film so she could get into the the good books of Yashraj Films as well as having the opportunity of working with Aamir Khan and Kajol. She would later act in Jhoom Barabar Jhoom (2007) which was produced by Yashraj Films.
When Kajol and her mother are on the train the poem they recite is from the 1976 film Kabhi Kabhie which starred Rishi Kapoor from this film as well as Amitabh Bachchan and Waheeda Rehman.
Rihan and Zooni meet in New Delhi on the occasion of Republic Day (26th January), but in all the scenes the people wear summer clothes, despite the fact it is very cold in Delhi in January.