Kal Ho Naa Ho clocks 15 years:These 10 lesser unknown facts about the Shah Rukh Khan starrer that will leave you shocked

Abhishek Bachchan and Vivek Oberoi were approached for Saif Ali Khan's role first. After they couldn't be signed for the film, Saif was roped in 

Preity Zinta's character 'Naina' was written keeping Kareena Kapoor Khan in mind, but when the latter demanded a high fee for the role, she was replaced by Preity

Karan Johar complied with international copyright laws and bought the license to the rights to Roy Orbison's 'Pretty Woman' which is featured in the film

The film was originally going to be shot in Toronto but eventually was shot in New York.

However, some parts of the song 'Kuch To Hua Hai' in the movie are shot in Toronto

The modifications and dresses of Jia's dolls in the film were made by Preity Zinta the day before the shooting of the scene

In the beginning we see 'Naina' running in a scene.

During the filming of the same Preity had fallen and injured herself. Director Nikhil Advani then got a model to jog in front of the camera instead

Karan Johar had first approached Ranbir Kapoor's mother Neetu Singh for the role of 'Jennifer' but that didn't work out. Eventually Jaya Bachchan played the role

'Kal Ho Naa Ho' was the last film to be produced by Karan Johar's father Yash Johar

It was during the shooting of 'Kal Ho Naa Ho' that Karan Johar's father Yash Johar was diagnosed with cancer.

While they were shooting for the film in NYC, Yash Johar was undergoing treatment in the same city.

In the film, we see Shah Rukh suffering and then finally dying of cancer

Although the film was Karan Johar's brainchild, he did not direct it. It was Nikhil Advani who cashed the opportunity and a directorial debut with the film