'Age of Ultron': Quicksilver and Scarlet Witch Are "Massively Important," Says Joss Whedon (Video)

Avengers Still - H 2015
<p>Avengers Still - H 2015</p>   |   Marvel Studios
"It's kind of just them against the world."

For fans paying close attention to the trailers for Avengers: Age of Ultron, one question has remained unanswered: Why, exactly, does the team decamp to a rural cabin where they all frown at each other? A new promo for the Joss Whedon Marvel movie explains everything — it's all the Scarlet Witch's fault.

Described by Whedon as "massively important characters," Scarlet Witch and Quicksilver are the focus of a new short featurette from Marvel Studios, introducing the troublesome duo to those unfamiliar with their comic book counterparts.

"He's fast and quick and anxious, and she's grounded and thoughtful," Elizabeth Olsen explains about her superhero alter ego and speedy sibling. But while the Witch might be thoughtful, it turns out that her specialty is disrupting other people's thoughts. "She messes with all the Avengers to such an extent that they have to go somewhere and come back as a unit," Olsen says.

It's not that she does so out of malice, however; as Aaron Taylor-Johnson explains, it's more that the Witch and Quicksilver just don't think they can trust anyone else. "They only have one another," he says. "It's kind of just them against the world." Of course, the world now includes killer robots voiced by James Spader, so things might be about to change….

Avengers: Age of Ultron is released May 1.

Read more Quicksilver Speaks in the New 'Age of Ultron' TV Spot (Video)