Joseph Gordon-Levitt describes how Bruce Willis paid him 'the highest compliment' while they made 'Looper'

Joseph Gordon-Levitt still isn't fully convinced Bruce Willis even did it on purpose. But one simple phrase – a string of just three words – from Willis left an indelible mark on him while the two were filming Looper, Rian Johnson's 2012 time-traveling thriller in which the actors played younger and older versions of the same character, Joe.

Gordon-Levitt even calls it "a moment of validation," having put in the hours attempting to embody "the spirit of Willis."

"There was [a] scene in the movie where we were yelling at each other," Gordon-Levitt shares in a new career retrospective interview with Vanity Fair. "I don't know if Bruce did this on purpose or he did it unintentionally, but it was kind of the highest compliment he could pay me. It was right after they said 'Cut.' He was turning away and walking back to his mark. He didn't even say it to me. He just kind of said to himself, 'Sounds like me.'

"And I just turned to myself and went, 'F***ing yes!' I think, knowing him, that was really his ultra-generous way of paying me a compliment, but it was very kind to do it in that way."

Though Gordon-Levitt doesn't mention it in the video, the anecdote carries heavier resonance in the wake of last week's announcement that Willis is indefinitely stepping away from acting due to the 67-year-old screen vet's battle with aphasia, a condition that affects one's ability to communicate. (The interview, released Wednesday, was likely filmed prior.)

Looper, Gordon-Levitt's second collaboration with Star Wars: The Last Jedi director Johnson after the filmmaker's 2005 debut Brick, remains a favorite for the actor for many reasons.

"One of my kind of marks of success as an actor for myself is, 'Do I seem different onscreen from myself?' It's probably why Looper's maybe my favorite performance of mine because it's the most different," he says. "Now granted, [I] sort of cheated, with the prosthetics… I get that thrill the most, 'It's someone else, it’s not me.'"

But if he "had to pick a favorite, just acting-wise, this is up there for me," Gordon-Levitt explained.

The makeup was indeed heavy for the 3rd Rock from the Sun alum, now 41.

“I wore hours and hours of prosthetic makeup every day to look a little bit like Bruce Willis. Kazuhiro Tsuji, the phenomenal makeup designer, told Rian and me that it was impossible to make me look like Bruce Willis, and he brought out charts," he said. "He brought out photos of Bruce and of me, and pointed out, 'Look, the distance between the bottom of his nose and the top of his lip… It's just not the same. I can't fix that. You will not get him to look like him.' And Rian [says] to Kazu, 'He doesn't have to look exactly like him. He just has to suggest it. It's OK. It's a movie."