One of the complaints about the first 'Avengers' movie was the lack of character development for the women, so writer-director Joss Whedon changed this in 'Avengers: Age of Ultron'.

Scarlett Johansson as Natasha Romanoff (Black Widow) in 'The Avengers: Age of Ultron'Scarlett Johansson as Natasha Romanoff (Black Widow) in 'The Avengers: Age of Ultron'

Scarlett Johansson's character Natasha (aka Black Widow) has the most engaging story arc this time. "It's nice to have substantial material," says Johansson. "The character is finally ready to make active choices in her life, and it's not great timing!"

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She goes on to say that she "loves that Black Widow is finally at a place where she can do something for herself, maybe a relationship. That's heroic in a big way and a small way."

Watch The Trailer For 'Avengers: Age Of Ultron' Here:

Over the past five years, Natasha has appeared in both 'Avengers' movies as well as 'Iron Man 2' and 'Captain America: The Winter Soldier'. "I've been really fortunate to build up this character to this point where I think I can now start to peel the layers away and reveal different sides of her," Johansson says. "I think I've been able to grow with the character, and the character's been able to grow with me."

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The other significant female role in 'Avengers: Age of Ultron' is Wanda (aka Scarlet Witch), played by Elizabeth Olsen making her first proper appearance in a Marvel movie after a post-credits cameo in 'Captain America: The Winter Soldier'. "It's a great balance of humour and action, with depth of character," Olsen says of the franchise. "This film especially highlights everyone's humanity and private lives."

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She was a bit intimidated by the size of the production and the high-profile cast. "But you get on set and you just have to have one thing that you hook into to give yourself that energy and the drive of your character," Olsen says. "We played with the idea of how much can Wanda do at the beginning of the film. At first it was not much, but as she understands her strength her abilities grow. And there's definitely a sense of confidence."

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As for pursuing the characters further, Olsen is returning for 'Captain America: Civil War' next year. And Johansson would be happy to explore the Black Widow further in a standalone movie. "That would be cool," she smiles. "I'm always happy to put the catsuit on."