If you've been keeping up with the previews, trailers and buzz surrounding "Looper," one of the many intriguing aspects of the Rian Johnson-directed time-travel thriller is actor Joseph Gordon-Levitt playing a young version of Bruce Willis. And even more intriguing than the concept of the talented "Dark Knight Rises" actor channeling Willis is how eerily similar the film's effects team was able to make Gordon-Levitt's face look, from the eyebrows to the lips to the ears.

MTV News recently caught up with the film's makeup artists Jamie Kelman and Kazu Tsuji to basically ask them one question: How the heck did they do that? Unsurprisingly, the answer is a complicated one that began when Gordon-Levitt contacted Tsuji, with whom he had worked on "G.I. Joe: The Rise of Cobra," and asked him if he could make him look like Willis.

"We had a meeting with Joseph and Rian Johnson and they told me about the story and who would be the older version of Joe, and when they told me that it was Bruce Willis, I thought it would be impossible because they don't look like each other at all," he said. "The proportion of their heads is different, and Joe's ears stick out more than Bruce's, Joe's eyebrows are higher than Bruce's, Bruce has a long upper lip and Joe has a short upper lip," he explained. The list of facial differences was so long that Tsuji initially tried to turn down the gig, but Gordon-Levitt and Johnson wouldn't let him.

"They really wanted me to do it," he said, agreeing to do one makeup test that involved full facial casts of each actor's face and head. "After I took life casts of Joe and Bruce, I started to sculpt and design the makeup, and what I made was a nose piece, an upper lip and lower lip, a vacuum foam plastic piece to pull back Joe's ears, a small hairpiece on the eyebrows to change Joe's eyebrows and contact lenses to change Joe's eye color. We did that first test makeup, and then I thought, 'OK, this might work,' " which led to a further development and design process that took about two months in total. After that, Tsuji handed off the on-set makeup-application duties to Kelman.

"As far as the daily application goes, Joe would come in for a little less than three hours, which included his wakeup ritual of shaving and generally preparing his face for the makeup," he said. "The makeup application itself would take two-and-a-half to three hours and 45 minutes. Some days went more smoothly than others. It's a very precise application of these things," Kelman explained, adding that it requires a committed and tolerant actor who has to want to wear the makeup or it doesn't work.

"If you have someone who doesn't want to do it or isn't into it, [the makeup] never ends up looking that great because of their energy or we're rushing it. You have to give this what it takes. It's kind of like baking: You can't take the bread out before it's done, and if you do, it's half-baked."

Both artists agreed that Gordon-Levitt was the perfect participant/recipient.

"He's awesome, we had a fun ritual," Kelman said. "Each morning, we would listen to an album and whatever album it was, Joe loves Radiohead, and we listened to the new Radiohead album, which came out during 'Looper,' so we'd listen to a full album and then we'd listen to a Stereolab podcast, and by the end of those two things, the makeup would be done, or if it wasn't, he would just doze for a little bit. You can't really sleep, because I have to ask him to turn his chin or his head. It's a tiring process, because you're sitting there for three hours expending energy, you're not unconscious. He was totally into the process, and because he was so into it is why it worked so well."

So what was the most challenging piece of makeup to apply?

"Application-wise, it's the lips," Kelman said. "The maintenance after a 14- to 15-hour day of shooting including lunch, the edges are where salad dressing goes. Joe was very respectful of the makeup, but at the same time, he didn't cease being a comfortable human being and resorting to Jamba Juice liquid diets or something. He ate real food with lips on, and that makes them fall apart a bit," he said. "Joe was good about being careful, but there is still a lot of maintenance involved. The lips were a challenge to keep looking good all day for the whole shoot. We had fresh sets for each day. I think it was almost exactly 50 [pairs]."

Check out everything we've got on "Looper."