Directed by S Shankar, the 2010 Tamil movie starred Rajinikanth and Aishwarya Rai Bachchan in lead roles.
"Shankar had come to me and he wanted me to play the villain in Robot. I called Rajini. He said, 'People will not accept you as a villain, so don't do it'. I said, 'Okay'," Mr Bachchan said in an interview in Mumbai.
There were reports that Big B was approached for Robot 2, but earlier, the veteran actor had dismissed any such speculation.
Meanwhile, Mr Bachchan will reportedly be a part of Dhoom 4.
Referring to this information, Big B said, "I heard it for the first time."
The 73-year-old actor will be next seen in Bejoy Nambiar's Wazir with Farhan Akhtar and Aditi Rao Hydari. He will also be seen in Sujoy Ghosh's Te3n and Aankhen 2.
"We will start Aankhen 2 in March. I play the same role," he said.
Aankhen, a 2002 thriller drama, was directed by Vipul Amrutlal Shah. The film was an adaptation of Mr Shah's Gujarati play Andhalo Pato.
Aankhen tracks the story of Vijay Singh Rajput played by Big B, a hard-working but temperamental man, who has spent all his life working for one bank and fetching them international recognition.
When Vijay loses his mind and goes on a violent rampage beating up another employee, he is subsequently fired. He decides to take vengeance by organising a heist, and having the same bank robbed by three blind men to avoid suspicion.