The Kabir Khan-directed movie, which hits the theatres on June 23, is set against the backdrop of the 1962 India-China war. While Sohail Khan is in the role of a soldier, Salman plays his simpleton brother.
The actor said the Shah Rukh didn't even listen to the entire conversation before saying yes.
"When Kabir narrated the subject to me, he said for this role we should get Shah Rukh. So, I called up Shah Rukh and told him, 'In Tubelight, there's this small', and he cut me, saying, 'It's done'. He didn't even let me complete the sentence. He just said 'it's done'," Salman told reporters here.
The actor was speaking at a special event last night where they introduced child actor Matin Rey Tangu to the media.
The five-year-old actor, who hails from Itanagar, plays an integral part in "Tubelight".
Salman said with "Tubelight", Tangu will become as popular as Harshali Malhotra, his co-star in "Bajrangi Bhaijaan".
The movie is an official adaptation of the 2015 American war drama "Little Boy".