When Hrithik Roshan watched Shah Rukh Khan and Amitabh Bachchan play the reconciliation scene he was so impressed and intimidated by the acting that he was unable to complete his own shot. He had to do it the next day after Amitabh had calmed him down and reassured him that everything would be fine.
This film bears some similarities with the director's previous film Kuch Kuch Hota Hai (1998): - The two pivotal lovers in both films are named Rahul and Anjali Sharma and are once again played by Shah Rukh Khan and Kajol respectively. - The first half of the film is told mainly in flashback structure ending in a character vowing to bring other characters together. - During a playful argument between Rahul and Anjali, Rahul snaps 'I don't like jokes' with Anjali replying 'I don't like you' in a mock voice. - "Suraj Hua Madham" contains a small melody from Kuch Kuch Hota Hai. - Rani Mukerji makes a small but important appearance in this movie, once again coming between the two lovers in the movie. - When Naina tells Rahul to follow his love, the theme song for Tina (Rani's character from KKHH) plays.
The character of Yashvardhan 'Yash' Raichand is modeled after the father of Karan Johar, the director of the movie, Yash Johar, who is also the producer of the film. The birth date of Yash Raichand that is mentioned in the movie is the same as Yash Johar's birth date.
Aamir Khan said in an interview with Karan Johar that when he saw Kabhi Khushi Kabhie Ghum at a special screening with the whole cast of the film, he hated the film so much that as soon as it ended he left as quickly as possible without congratulating any of the cast and tried to avoid Karan Johar and Shah Rukh Khan. However, he apologized to Johar on his show Koffee with Karan, and the two laughed and made up.
The trivia item below may give away important plot points.
Parzan Dastur, who plays Ashfaque's nephew in Kabhi Khushi Kabhi Gham also played Silent Sardarji in Kuch Kuch Hota Hai. In Kabhi Khushi Kabhi Gham, during Rukhsar's wedding, he is seen counting stars, the same thing he does in Kuch Kuch Hota Hai.