Elizabeth Olsen is nervous about starring in Avengers: Age of Ultron.

The 25-year-old actress is one of the new stars to join the cast of the superhero movie - in which she will play the Scarlett Witch, alongside newcomer Aaron Taylor-Johnson, who will portray Quicksilver - and worries she has not had the same opportunity for character development as returning cast members.

"It is intimidating going into a production where everyone has their characters fully fleshed out and they know their weaknesses and they have their comedy. Aaron and I don't really have the luxury of time to develop those," she said.

The returning cast includes Robert Downey Jr. as Iron Man, Chris Hemsworth as Thor, Mark Ruffalo as The Hulk, Chris Evans as Captain America, Scarlett Johansson as Black Widow, Jeremy Renner as Hawkeye and Samuel L. Jackson as Nick Fury.

Elizabeth added she can't wait for the full cast to get together for the press shot to promote the movie. "I'm so excited for that to happen. I really am having so much fun," she added.

The Godzilla actress is also pleased about getting to work with director Joss Whedon on the project, because of his enthusiasm and the way he likes to let characters develop naturally: "I am unique in this world, and so it's fun to do what I get to do, because it is different. And I think it also is fun for Joss because we're developing and creating something together, and he's getting really excited by it."