When you were 12 years old, what were you doing with your life? To most, it's a time to play in the park, fantasize about cloud shapes, and watch a lot of "SpongeBob SquarePants." To Chloe Moretz, the tween years are a good time to launch a Hollywood career -- and kick some ass.

"Basically, Aaron Johnson plays Kick-Ass," the "(500) Days of Summer" star explained to us while discussing her new movie that seems likely to make her a household name before she even has a driver's license. "He's a regular, everyday kid -- a nerdy comic book fan, and he's like, 'Why doesn't anyone ever try to be Batman? Just a normal guy turned hero?' So he goes out, tries, and gets totally beaten up; he gets stabbed and then run over by a car. ... That's when Hit-Girl and Big Daddy come in."

Moretz is Hit-Girl -- the C-bomb-dropping, gun-toting tween who wages war against the mob alongside her [article id="1635853"]Batman-obsessed daddy, played by Nicolas Cage[/article]. The first time you see the duo onscreen, Big Daddy is firing bullets into the little girl's chest -- and from there, things get

violent.

"We show up at [Kick-Ass'] house, say, 'We know about you,' and he realizes we're real vigilantes," Moretz said of the plot, based on the beloved comic book of the same name. "I've been trained since I was a baby to be this crazy assassin girl. But what I like about the character is that she's an assassin, but at the same time she is still just an 11-year-old girl. She doesn't know any better; it's just how she was raised."

Count

EWS/100419986" target="_blank">Roger Ebert among those who seem bothered by Hit-Girl's ruthless nature and the jokes that often come from it. But according to Moretz, all that ass-kicking is part of the character, and nobody should get too hung up on it.

"It's a movie; it's not me," she explained. "If I ever uttered one word that I said in ['Kick-Ass'], I would be grounded for years! I'd be stuck in my room until I was 20!

"I would never in a million years say [what Hit-Girl says in this film]," she laughed. "I'm an average, everyday girl; when I act with my friends, I'm totally immature. ... I have to go to bed at 9:30. If I'm up late on the computer, I lose it for two months."

This week, li'l Chloe is appearing all over the talk shows; she has recently signed on to "The Fields" with Sam Worthington and "The Invention of Hugo Cabret" for Martin Scorsese. Later this year, she'll return in a controversial remake of the Swedish vampire classic "Let the Right One In," and director Matt Reeves is already [article id="1636133"]calling her performance "primal."[/article] Couple all that with the fact that Hit-Girl seems likely to be this year's hot Halloween costume, and you can see how a 13-year-old girl could get a big head -- that is, if she was anyone other than Chloe Moretz.

"My mom and my dad, they keep me totally grounded," she promised when she dropped by our studio with no entourage and only her parents in tow. "My mom has always said that if I get a big head, she'll take me out of this business as quickly as I got into it."

Check out everything we've got on "Kick-Ass."

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