Hrithik Roshan and Kareena Kapoor were to make their debut in Rakesh Roshan's Kaho Naa... Pyaar Hai.

But destiny had other plans for Kareena. Differences between Roshan Sr and her mother Babita saw Kareena drop out of Kaho Naa... after a few days of shooting. Amisha Patel subsequently replaced her.

Kareena then went on to make her debut opposite Amitabh Bachchan's son Abhishek in J P Dutta's Refugee. But curiosity to see a striking pair had been aroused.

Directors began to invent ways to cast Hrithik and Kareena together. The first was filmmaker Subhash Ghai. But Yaadein bombed, mainly because neither of the young actors was presented in pivotal or coherent roles.

Another opportunity presented itself when Karan Johar paired them in Kabhi Khushi Kabhie Gham. Though Hrithik and Kareena had to take a backseat with Shah Rukh Khan and Kajol taking centrestage, the duo managed to whip up a striking chemistry within the limited arena.

After K3G, they were paired again in Kunal Kohli's Mujhse Dosti Karoge. Although the first half of the film saw Hrithik woo Kareena in style, it was ultimately Rani Mukerji whom he ended up losing his heart to.

Sooraj R Barjatya's Main Prem Ki Diwani Hoon is a tribute to the chemistry between the couple, though they are yet to achieve the level of success Shah Rukh Khan and Kajol (Baazigar, Dilwale Dulhaniya Le Jayenge, Karan Arjun, Kuch Kuch Hota Hai, K3G) did as a pair.

In the past, Raj Kapoor and Nargis were the first couple to warm the screen in a cluster of films in the 1950s, especially Awaara. Two decades later, Rajesh Khanna and Sharmila Tagore exuded the same level of intensity in a series of romances starting with Aradhana.

A few other couples who set the screen on fire were Dilip Kumar and Madhubala in K Asif's Mughal-e-Azam, Dharmendra-Meena Kumari in Phool Aur Patthar, Amitabh Bachchan-Raakhee in Kabhi Kabhie, and Shah Rukh Khan-Kajol in Dilwale Dulhaniya Le Jayenge.

Whether it is the beach serenade O ajnabee or the Valentine's Day number Sanjana I love you, Kareena says, "We [Hrithik and Kareena] are supposed to be intensely in love. Unless the depth of our feelings shows up on screen, audiences won't flow with the emotions in a love story."