"What a sensational day in the studios of KBC! A young man from the interiors of Bihar, earning a meagre salary of just Rs.6, 500 per month, coming from the most humblest of backgrounds, reaches the hot seat and cracks the ultimate prize - 5 cr rupees! An incredible feat!" Amitabh posted on his blog.
"This is what the common man is all about. This is what KBC is all about - given an opportunity, the common man has the strength the ability and the accumen to prove to the world that he is the best and second to none, " added the 69-year-old Bachchan, who hosts KBC.
Kumar is a computer operator and tutor. His victory led to celebrations on the sets of the show.
"The pulsating excitement on the set and among the crew was unimaginable. It was as if they had won the hugest prize ever in the history of Indian television.
The tension as each question was meticulously answered and the pulsating and throbbing hearts as he crossed the Rs.1 crore mark and then waited and waited and waited till almost eternity to decide on that final answer of Rs.5 crorer.
"The entire place just exploded. The family of Sushil Kumar, the contestant, not prone to any kind of public jubilation ran on to the floor of the set in uncontrollable joy and screams and tears of happiness, whilst the live audience were whooping it up on their feet with the loudest scream I have ever heard in this 11-year association with KBC!"
In the past, the first season of "Kaun Banega Crorepati" saw Harshvardhan Nawathe from Mumbai walking away with Rs.1 crore.
In 2004, Rahat Taslim from Jharkand won Rs.1 crore but quit before the jackpot question for Rs.5 crore.
The episode, featuring Kumar's win, will be telecast Nov 2.