Though Robbie as Barbie was a given, Gerwig wrote the role of leading-man Ken for Gosling with no assurance whatsoever that he would be willing or able to do it.
“I just knew he would be perfect for this,” she recalled to E!. So when the producers saw Ryan’s name written into the script, “they said, ‘Oh, that’s great, you know Ryan,'” she continued. “I was like, ‘Oh, no, I’ve never met Ryan. I don’t know if Ryan will do this, I just want him to.’ I feel like I sort of conjured him out of thin air. But I can’t believe he said yes and then I can’t believe he gave the performance he gave.”
The performances that both he and Robbie gave, the director was quick to add.
“I knew they were great but every day I found myself floored,” Gerwig said. “They allowed the comedy to come out of taking it very seriously. They never made fun of it, they never stood outside of it. They always came at it with just total commitment and truth—and that’s why it’s funny. But there are definitely moments in this movie where I just can’t believe they did it. I still can’t believe they did it!”