This incident happened on the sets of Merchant Ivory productions Bombay Talkies in 1970.
Shashi Kapoor was the lead actor of the film and this was the time when Amitabh Bachchan was struggling as an actor to get work. Amitabh Bachchan tells us that he was told that he has to be part of the crowd and he will be paid for that so he agreed our of desperation even though he was playing an extra in the crowd. In the film’s last scene when Shashi Kapoor’s funeral scene was picturised Amitabh was part of the crowd. So the crowd scenes were shot without Shashi Kapoor.
When Shashi Kapoor came to set, he was surprised to see Amitabh Bachchan there. He asked him what is he doing there? Amitabh told him he is working as extra for some money. Shashi Kapoor became livid and he scolded Amitabh that he should not ruin his career by doing bit roles as he is meant for bigger things given his performance in his debut film Saat Hindustani which had fetched him a National Award. So why should he work as an extra? Shashi Kapoor got that scene removed from the film.
It was not just Shashi Kapoor but the great director Hrishikesh Mukherjee who believed that Amitabh Bachchan was meant for bigger things. During the same time Amitabh Bachchan was signed by Mukherjee for Guddi, even though it was a heroine centric role and the make lead was a small role. A few months later Amitabh’s and Mukherjee’s film Anand released and became a cult film. Hrishikesh Mukherjee realised that Amitabh has much more potential which should not be wasted in a small role like Guddi. So he asked him to leave the film and do bigger films (Hrishikesh Mukherjee eventually gave him many defining roles of his career including Namak Haraam, Abhimaan, Chupke Chupke etc).