The son literally is the father in this film in which Abhishek and Amitabh Bachchan switch their real and reel roles. The premise sounds confusing, until the exclusive preview of Paa at the Screen Preview on Thursday cleared up doubts. Present at the event were the director of the film, Balki, and the two main protagonists, Abhishek Bachchan and Vidya Balan.

Paa, which is based on the life of a patient who suffers from progeria — a condition in which aging is accelerated — is a tribute from Abhishek to his father. “I just wanted to make this film for my Paa,” he says, referring to the Big B.

When Balki first came to the Bachchans with the script about a father-son relationship, they did not think it was particularly unique. “But when Balki told me that I would be playing Amitji’s father I was completely taken aback. It was an opportunity of a lifetime and I must say I enjoyed playing Paa’s Paa,” said Abhishek.

For Balki, who had worked with the Bachchan Sr in Cheeni Kum, the main aim was to get the father-son duo together in a film. “It was then that I read up about progeria, did research and came up with this script,” says Balki.

For Vidya Balan, too, the film was a unique experience. “I did not know how I would pull off playing a mother on screen. But when Amitji got his make up done and came on to the sets, we just clicked. It was wonderful.”