In the film, Gordon-Levitt, 31, plays an assassin who’s hired out to kill victims sent through a time machine, only to find that he’s latest target is actually his future self (played by 57-year-old Willis).
Celebuzz caught up with the actor — and his costar Emily Blunt — at San Diego’s Comic-Con where the star spilled on how he prepared for the part.
“I didn’t work out at all,” he told Celebuzz. “But I did just do a part where I worked out.”
How does Gordon-Levitt — who’s starred in action-thrillers like Inception and The Dark Knight Rises — bulk up for a role?
“Just classic meathead behavior: going to the gym everyday and eating a lot of chicken,” he said.
Curiously, his costar Blunt, 29, asked, “Do you do the eggs like Rocky?”
“Not raw,” Gordon-Levitt replied, smirking. “I did eat a lot of eggs but they were scrambled.”
The two stars were at Comic-Con — famous for embracing the comic book culture — to promote Looper, though they spilled that they’re really geeks of something else.
“I really geek out over music,” Blunt told us.
So has her husband — The Office‘s John Krasinski — taken her to any concerts yet?
“He has and it’s been a mess,” she said. “He does not do that anymore.”
As for Gordon-Levitt’s geeky obsession? Watch our interview with the star — above — to find out.
Looper hits theaters Sept. 28.