The film screened Saturday at the Tribeca Film Festival, where Levine said he had to leave his comfort zone for his first acting experience.
"I kept telling her she was great and she wouldn't believe me, and she told me that I wasn't bad at acting either but I didn't believe her, so it was perfect," he said of working with Knightly.
"I was completely terrified," Knightley said. "I didn't anticipate being as frightened as I was. I said yes to doing it and I was, 'Oh, it's gonna be fine, it's gonna be fine,' and then suddenly I found myself in a studio with real people who did it for a living and I was like, 'I don't know what I'm doing. I'm pretending.' "
Ultimately Levine said it was a positive experience.
"My experience was so much fun," he said. "It made me kind of start to like it a little bit, but I don't know. I don't think you can really make those bold declarations, but we'll see."
Notable deaths of 2014 [PHOTOS]