Being Bruce Willis isn't easy. Especially when you're actually Joseph Gordon-Levitt.

Gordon-Levitt, 31, plays Willis' younger self in the time-traveling, mind-bending film "Looper," out today.

The illusion entailed three hours a day in a makeup chair.

The nose was altered, the lips thinned, with makeup and prosthetics. Brown eyes were made blue.

Such attention to detail was vital because younger and older versions share the screen in "Looper," in which Gordon-Levitt plays an assassin of criminals who are sent back in time, to their deaths, from the future.

"It is me sitting across the table from my future self," Gordon-Levitt said of a scene with Willis. "It required a transformation."

To prepare, "I studied him quite a bit and watched his movies, and I ripped the audio off his movies," Gordon-Levitt said by phone from San Francisco during a publicity stop with "Looper" director-screenwriter Rian Johnson.

Willis helped by recording himself reading Gordon- Levitt's voiceover parts, for the younger actor to study.

Willis was cast long after Gordon-Levitt, star of Johnson's acclaimed 2005 high school noir "Brick." Johnson had written the role of "Joe" with his good friend, Joe, in mind.

Getting Willis to sign on was "a grand, victorious fist pump for us," Gordon-Levitt said.

But it posed a challenge.

"Once we cast Bruce, I thought, 'Oh no, they look nothing alike,' and was a little bit panicked," Johnson said.

Gordon-Levitt's approximation of Willis went well beyond prosthetics, Johnson said.

"He did this magic trick where he created this living, breathing character who is not just a 'Saturday Night Live' impression," Johnson said.

Gordon-Levitt can do "Saturday Night Live," too, as he showed last week with his all-out "Magic Mike" spoof on the show. Such are the chameleonlike charms of the one-time teen actor from the long-running NBC sitcom "3rd Rock From the Sun."

With key supporting roles in director Christopher Nolan's "Inception" and "The Dark Knight Rises," and starring roles in "Looper" and the recent bike-messenger movie "Premium Rush," Gordon- Levitt blows up the idea that all child stars end up in rehab or on reality shows.

His rise appears seamless because he made his cinematic mark first in small films such as "Brick" and the Gregg Araki film "Mysterious Skin." Gordon-Levitt's sensitive portrayal of a hustler in the latter film lifted him to the Ryan Gosling ranks of respected younger actors.

Gordon-Levitt broke through in a big way in 2009 when he mixed his penchant for indie film with his natural whimsy in "(500) Days of Summer."

Johnson, 37, said he was not surprised by Gordon–Levitt's ascent in the years after "Brick."

"You never know, career path-wise, but I did absolutely see a young man who was making decisions for the right reasons and choosing roles he took based on who he wanted to work with," Johnson said. "(His success) makes sense to me, and it is really nice to see someone succeed on that level, especially when you feel like they are doing it right."

Even at Gordon-Levitt's level, scripts aren't necessarily being written with him in mind.

It happened with "Looper" partly because "Rian is one of my best friends," Gordon-Levitt said.

"So it would have been really awkward if the script wasn't good," he joked.

"Looper" pairs Gordon-Levitt in several scenes with child actor Pierce Gagnon, whose character is key to the movie.

"He is such a great actor – and he was 5 when we shot 'Looper,' " Gordon-Levitt said of his young co-star. "I was 6 when I started acting, so I never treated him like a kid. I remembered when I was a kid, and I didn't like it when people talked down to me."

His experiences have made him "picky" about juvenile performances, Gordon-Levitt said.

"What happens a lot for me is, if I see a movie with a kid's performance, I will say, 'Oh, I don't really believe it,' " Gordon-Levitt said. "Friends will say, 'But it's just a kid.' (But) I expect kid actors to have the capability to be the best around. They are closer to that uninhibited place we all start out with, without the self-consciousness."

Gordon-Levitt next will appear in Steven Spielberg's "Lincoln," his most prestigious movie to date. He plays Robert Lincoln, eldest son of Abraham and Mary Todd Lincoln (Daniel Day-Lewis and Sally Field).

"Lincoln" focuses, Gordon-Levitt said, on the month during which President Lincoln was trying to get passed the constitutional amendment to end slavery.

"Their relationship was a bit strained," Gordon-Levitt said of the Lincoln father-son bond. "The Civil War had been going on for years and was obviously straining, and Robert wanted to enlist but was being kept out because his mother did not want him in the Army. Every young man in the country was fighting in the war and to be kept out of it really made him feel like a coward."

"Lincoln" comes out in November. In the meantime, Gordon-Levitt is polishing his status as Internet darling.

His duet with "(500) Days" co-star Zooey Deschanel on "What Are You Doing New Year's Eve?" showed off his singing voice and became a viral sensation last year. His collaborative website and production company hitRECord produces other videos as well as books, records and live musical showcases.

"It is such a unique process," Gordon-Levitt said of creating works via hitRECord, which encourages input from filmmakers, musicians, animators and other artists. "I am so proud of it."

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