According to trade analyst Vinod Mirani, an unusual pairing will definitely become a hit formula but cautions that such experiments need a convincing script.
"An unusual pairing works only when it is needed. When the story demands it, then it looks authentic. Or else one can't just force unusual pairs in a film to make it look different," Mirani told IANS.
So far, one of the most successful unusual pairs has been of Rahul Bose and Mallika Sherawat. They teamed up for Pyaar Ke Side Effects and were instant hit at the box office as the people adored their romantic escapades in the rom-com.
When Amitabh Bachchan was paired opposite much younger Tabu and Jiah Khan in Cheeni Kum and Nishabd respectively, critics were sceptical about viewers' reaction. But much to their surprise, audiences enjoyed watching Big B romancing Tabu and they also appreciated his pairing with Jiah. It was so because it fitted into the scheme of the story.
A typical pairing that saw high popularity was when heartthrob Ranbir Kapoor and Konkana Sen Sharma came together in Wake Up Sid. Not only did audiences enjoy their on-screen chemistry, the film too turned out to be one of the biggest successes of 2009.
"At times it works at times it doesn't. The story has to be conniving like 'The Dirty Picture' or 'Kahaani', where it should be justified," said Mirani.
The 44-year-old Akshay Kumar, who teamed up with 25-year-old Sonakshi Sinha in recent hit Rowdy Rathore, says age doesn't matter while finalising the cast.
"Age is just a number. Even today I can run better than a person who is half my age. Also, if these young girls look great with us, then what to do?" said Akshay, who will again be seen with Sonakshi in Joker.
Sonakshi Sinha, who started her career with much older Salman Khan in Dabangg, says chemistry is more important than anything else.
"There is nothing like that, one should not think about it (unusual pairings) so much! After all, the chemistry looks awesome on screen and we saw that in 'Rowdy Rathore', isn't it?" she added.
"Shaadi Ke Side Effects" is a sequel to "Pyaar Ke Side Effects" and Nandy said that it needed a fresh pair.
"This film demanded fresh faces. We always had Vidya in our mind for 'Shaadi Ke Side Effects'. I believe she really liked the script," he said.
Not only Bollywood, even the southern film industry is trying out the formula and the most recent example is upcoming Tamil period film Kochadaiyaan, where Deepika Padukone will be seen romancing southern superstar Rajinikanth.