Joseph Gordon-Levitt "studied" Bruce Willis before working on 'Looper'.
The 'Dark Knight Rises' actor admits he watched a host of Bruce's films to try and get into his psyche as they both were playing two versions of the same man in the sci-fi action movie.
He said: "I just studied Bruce. First just studying his movies - I'd rip the audio off the movies and listen on repeat.
"He even recorded himself doing some of my voiceover monologues and sent that to me. But I think the most important thing was just hanging out, spending time together, getting dinner and letting it seep in."
Joseph was particularly enamoured with the idea of the film as it provides answers for questions all people have throughout life.
He said: "At the crux of it it's a story about what you would say to your future self, or to your past self, if you could actually meet them and have that conversation.
"Obviously that can never happen in real life, and that's the beauty of science fiction, that it can dramatise that."