Joseph Gordon Levitt says that he studied Bruce Willis as he prepared for the role.
Levitt and Willis play the young and the older version of the same character in their new movie Looper and Levitt admits that it was important to get to know his co-star.
Speaking to Digital Spy the actor said: "I just studied [Bruce]. First just studying his movies - I'd rip the audio off the movies and listen on repeat," he said.
"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."
Looper reunites Levitt with director Rian Johnson while he is working with Willis for the very first time.
It has already been a busy summer for the actor after being part of the ensemble cast for The Dark Knight Rises before going on to Premium Rush.
Looper is released 28th September.