IT WOULD be too easy to dismiss Reese Witherspoon as another Hollywood blonde. While the Southern belle’s impish looks could have guaranteed her a success in romantic comedies, Reese has chosen a more unconventional path.

From Pleasantville, about a pair of 1990s teenage siblings who are magically transported into 1950s, to her performance as June Carter Cash in the critically acclaimed Walk The Line, Reese has been drawn to unconventional roles.

Her latest challenge, voicing the part of Susan/Ginormica, a girl- turned-monster in new 3D animation Monsters vs Aliens, reflects her tendency not to fit in.

Susan is an ordinary girl planning her wedding when she is hit by a meteorite and turned into a giant. She is then dragged off to a secret government compound and has to fight evil aliens that are trying to take over the world.

Along the way Susan has to come to terms with who she is. As if that wasn’t enough, Susan is locked in the compound with other monsters. At first she is repulsed but as the film goes on she learns to love them.

"Through the journey of the film, Susan starts to value and appreciate the monster crew for the support that they give her – the love, the companionship, the understanding that they have of the situation," Reese says.

"She has come to terms with the fact that she can’t really go home again in the same way. She’ll never be just Susan Murphy from Modesto.

"Through the help of the Monsters, she realises it’s a little awesome to be different. They all value each other for their qualities, and they form this offbeat family."

The film’s powerful message about being an outsider was partly what drew Reese to the role.

"I think it’s great that this movie has a message that no matter how weird you feel you definitely have a place in this world and sometimes that can be your greatest benefit," she says.

"I thought it was a great evolution of a character who starts out as sort of this 1950s, very innocent, sweet girl and she has to find her inner strength to realise she has to be responsible for herself and ultimately save herself and save the world."

However much she loved the script, being a giant superhero was tough for 5ft 1in Reese, who had to channel all her efforts into sounding like she could take on an evil alien.