For the preparation of the role 'Surya' went to hospitals and met patients with memory problems. He observed how they behave and react. He also video taped various patients from those hospitals and repeatedly watched them, for the character finalization.
Director A.R. Murugadoss' was approached to remake it on Telugu, but declined saying that he can create magic only once. Later when Aamir Khan requested him to adapt it on Hindi, he accepted his offer.