Tom Cruise may have never starred in “Rain Man” if not for his little sister.

During a wide-ranging conversation at the BFI in London on Sunday, Cruise reflected on the films that made his career and told the story of his chance meeting with Dustin Hoffman at a New York City restaurant. It was 1984 and Cruise had just shot Ridley Scott’s “Legend.” He was back in the States visiting his sister Cass, who spotted Hoffman from across the restaurant.

“She goes, ‘There’s Dustin Hoffman.’ I looked up and there he was, in a hat — he was doing ‘Death of a Salesman’ — and he was ordering takeout,” Cruise said. “She goes, ‘You go over there and say hello to him.’ I was like, ‘I’m not going to say hello.’ She goes, ‘You know him, you know his movies.’ And she doesn’t do stuff like that. And I...