Hum Tum was a game changer for Saif Ali Khan but Hrithik Roshan was the first choice for the role.
As Hrithik was going through a rough patch with flops like Naa Tum Jaano Naa Hum, Aap Mujhe Ache Lagne Lage and Main Prem Ki Deewani Hoon he was a bit skeptical to give it a nod. Though he loved the script, he was not sure whether it will be a right choice.
After Hrithik, it was Aamir Khan who was approached for the same. It was the time when Aamir was going through his divorce with Reena Dutta. He was not in the right frame of mind for a rom-com and did not even hear the script.
Vivek Oberoi who was gaining popularity with Company and Saathiya liked the script. He even alloted dates for the film but cancelled them later demanding some changes in the script. Further, there were some more issues and the makers decided to move on.
Finally, it was Saif Ali Khan who made it. Hum Tum helped Saif to come out of the image of a supporting actor and established him as a solo hero. His performance was appriciated in the film. Hrithik watched the trial of the film and he too felt that Saif was the right choice.
Aamir Khan was already a huge name a much ,much bigger star than SRK and 4 years his senior
Not a rank newcomer like SRK after Deewana
He already had Qayamat Se Qayamat Tak
Qsqt halter the action hero era of Amitabh Bachchan and Dharmendra
Which was copied by the likes of Anil Kapoor and Mithun Chakraborty.
Dil which outgrossed Ghayal Sunny Deol who was the biggest superstar of the era
Dil Hai Ki Manta Nahi
&
Jo Jeeta Wohi Sikandar
Even SRK said he watched Qsqt in college
SRK movies like Raju Bangaya Gentleman
And
Kabhi Haan Kabhi Naa
Were Aamir Khan rejects even Juhi Chawla when asked about the newcomer for Raju Bangaya Gentleman was said that he's like Aamir Khan
After the huge flop which was Lamhe Yash Chopra and Aamir Khan worked together in Parampara
Yash Chopra's first movie after Deewar which produced by an outside producer
Deewar by Gulshan Rai
And Parampara by Feroz Nadiadwala
Aamir Khan already a young superstar wanted a join narration with Sunny Deol
He was not okay with the fact that Sunny Deol would beat the shit out of him like he did too SRK in the movie he wanted a equal fight and Juhi Chawla killing his character.
He even said he didn't reject Darr he was removed from it.
There was news that Anushka Sharma auditioned for the role of Pia. However the audition video that was viral was of Munnabhai M.B.B.S. Also Kajol was supposed to play a role or a cameo in the movie but later turned down.
Aamir Khan became the first and only actor to kiss Kapoor sisters (Karishma in Raja Hindustani and Kareena in 3 Idiots).
Aamir Khan plays a college student in the film but in real life he is just five years younger than Boman Irani who plays the role of VIRUS in the film. Similarly, Ali Faizal who plays the character of Joy Lobo in the film is shown senior to Aamir Khan but in real life he is 23 years younger than him.
The pregnancy scene was actually planned for Munna Bhai M.B.B.S but Rajkumar Hirani changed his mind and years later used it in 3 Idiots.
Shahrukh Khan who chose My Name is Khan referred himself as the fourth idiot for not being a part of such a great movie.
Kareena Kapoor wanted to work with Rajkumar Hirani and she herself approached him for the role.
Boman Irani initially refused to play the role of VIRUS and even recommended Irffan Khan's name but later agreed to be a part of the film.
The song “Zoobi Doobi” is actually a tribute to Raj Kapoor and his hit song “Pyar Hua Ikraar Hua” from Shree 420.
According to Rajkumar Hirani the original cast of the film was Shahrukh Khan, Saif Ali Khan and John Abraham.
At one time there were reports that Hrithik Roashan, Abhishek Bachchan and Saif Ali Khan were considered for the film.
Aamir Khan and Javed Jaffrey did not share a single scene together in the film. Before this they were seen together in one film which released in 1990 and was titled, “Jawaani Zindabad”.