Generally when a romantic film becomes a blockbuster the pair is repeated again and again to encash their popularity. But there is a rare case when a romantic pair was never repeated despite delivering the biggest hits of their career.
Aamir Khan and Karishma Kapoor
Both of them had worked together in Andaz Apna Apna together in 1994 but they were not paired together. So the only film they co starred was Raja Hindustani. A mix of Jab Jab Phool Khile and Pyar Jhukta Nahin this film was a massive blockbuster earning 45 crores nett and was the highest grosser of 1996 and 4th highest grosser of the entire 90s (After HAHK, DDLJ and KKHH). Both the actors won the Best Actor and Best Actress Filmfare Respectively. And despite all this they never worked together again.
After the success of Raja Hindustani Karishma Kapoor became the number 1 actress of the industry and decided to be choosy with her films. Aamir was already known to be a choosy actor. After she won a National award in 1997 she became even more choosy and didn't had any release in 1998. And since 2000 she chose to work in heroine centric films like Fiza, Shakti, Zubeida. And the only other director Shekhar constantly worked with was David Dhawan. Aamir offcourse never fit in the mould of David Dhawan movie.
So we could never saw this very successful pair together again.