"I think he was just joking. He replied to a query. I don't think he was serious," Mahadevan told PTI here.
"Let me do something which will make every Indian proud and then somebody can make a biopic on me."
Mahadevan was a guest in Ghai's film school when the filmmaker expressed a desire to make a biopic on the musician.
Of late, biopics like "Mary Kom", "Paan Singh Tomar" and "Bhaag Milkha Bhaag" have done well in Bollywood and a number of real-life inspired movies are in the pipeline including a film on Mahendra Singh Dhoni, Azharuddin and Sarabjit Singh.
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This is the second song, after 'Sarfira', that has been launched by the filmmakers, Mahadevan said.
"'Sau Asoo' comes towards the climax of the film when Imran Khan breaks up with his live-in partner Kangana Ranaut in the film.
"Sau Aasoo shows how much Imran is in love with Kangana and how his life is affected after the breakup," he added.
The song has been composed by Shankar, Ehsaan and Loy and sung by Rasika Shekhar and Shankar. The lyrics have been penned by Kumaar. The composers also gave a preview of the song before the makers launched it.