Lady Gaga was a real pro as she filmed the Sin City sequel, Joseph Gordon-Levitt has revealed.
Joseph, who will take the lead role of gambler Johnny, admitted he was really impressed by the Applause singer, who makes a cameo in Robert Rodriguez and Frank Miller's new film, Sin City: A Dame To Kill For.
He told US radio show Jam'n 94.5: "Lady Gaga is in a scene and I gotta say, she did a really good job. She's a great actress and I didn't know that.
"I was like, 'OK, sure, they're having a huge pop star do a scene in the movie, I understand.' But then she came in and, like, nailed it. She had her character down, and she was like a total pro, and did a great job, I was really impressed."
Bruce Willis, Jessica Alba, Rosario Dawson and Mickey Rourke will return for Sin City 2, which is being shot in 3D and is set for release in August 2014. Josh Brolin, Ray Liotta, Jeremy Piven and Juno Temple appear in the film noir adaptation of the graphic novel.
As well to her cameo in Sin City 2, Lady Gaga - whose real name is Stefani Germanotta - will make her big-screen debut as La Chameleon in Robert Rodriguez's Machete Kills.
Joseph, who next makes his directorial debut with Don Jon, also confirmed that he won't be reprising his Dark Knight Rises role of Robin John Blake and his superhero alter-ego Nightwing.
Asked about a spin-off movie, he said: "Not that I know of. I think it's a really good ending to that trilogy."