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Dave Lizewski, played by 19-year-old Brit Aaron Johnson, is the ordinary New York teenager who buys a wetsuit from the internet to become the latest Hollywood superhero Kick-Ass.

He thinks that comic books have it wrong and that people don't need a power to be a superhero.

The film of the same name originally started life as a comic book: "That's where it comes from", explains Aaron Johnson.

"There's a mad comic book following in America. We wanted to make this one as true to the comic book as possible."

The screenplay for the big screen version was co-written by director Matthew Vaughn and Jane Goldman (Jonathan Ross's wife).

But Johnson says the characters are a long way from the invincibility of Superman.

He said: "The whole concept of it is people dressing up as real superheroes and going out and fighting crime.

"These kids get a really hard punch or bullet to the chest they can die. It's real and you can relate to it."

Lizweski hits the streets of New York to fight crime but soon has competition in the form of father-daughter crime fighting duo, Hit Girl & Big Daddy (played by Nicolas Cage).

"Working with Nicolas Cage was inspirational," says the actor.

"The guy brings his character to life - way off the page. He's bold, out there, pretty wild."

In pictures: Kick-Ass premiere

Chloe Grace Moretz plays Cage's daughter, Hit Girl. She's one of the toughest characters in the movie and the 13-year-old says she loved getting involved with all the rough and tumble.

She said: "I learnt how to shoot the guns, how to do martial arts, how to throw knives... doing all the action was so, so fun. I loved it!"

Hit Girl aside, does Moretz have any super hero aspirations? "If I could be another superhero I'd be Batman," she admitted.

"He's a lot like Hit Girl in a way. They both don't have powers but they're vigilantes and they fight crime. They're a lot alike."

Every superhero needs an arch-enemy and the unlikely saviours in Kick-Ass join forces to battle Mafia boss Frank D'Amico and his son Chris, aka Red Mist.

Chris Mintz-Plasse who plays the character reckons the movie isn't likely to inspire any real life vigilante superheroes,

"I think they'd be silly. In the movie he first gets stabbed and gets put in a coma for a couple of weeks.

"That's not a good sign. I don't think anyone's going to see the movie and say, 'I want to be a superhero after this!'"

Kick-Ass is released in the UK on 26 March.