Brother and sister duo Pietro and Wanda Maximoff, a.k.a Quicksilver and Scarlet Witch, are two of the most notable characters being introduced in Avengers: Age of Ultron, arguably preceded only by the titular villain himself. Beyond their long history with the team in the comics, director Joss Whedon felt it was necessary that these two be present in the story.
Despite finding out that the X-Men film series was using Quicksilver soon after Avengers: Age of Ultron planned to use him, Whedon told Rolling Stone that their version of the siblings not only gives Ultron someone to talk to (since his drones aren’t good for conversation), but also add something special to the story, calling their relationship "sweet and different and strange." In Whedon’s words:
We need them because their powers are different, their looks are different, and their opinion is different. They will be young, fresh, and interesting.
Although the Avengers feature a juiced-up super-solider, a scientist who turns into a green rage monster, and a Norse god who can harness lightning, Whedon is right saying that their powers are unique. Origin-wise, the siblings’ abilities are awakened after being subjected to Loki’s scepter by Baron Strucker and HYDRA. The result is Pietro (Aaron Taylor-Johnson) discovering he can move at superhuman speeds, while Wanda (Elizabeth Olsen) finds herself with abilities like telekinesis and hypnosis. While both will cause problems for the team, Scarlet Witch’s abilities will put several of the Avengers through the ringer, like driving the Hulk insane with anger, which forces Tony Stark to put on the Hulkbuster suit to deal with him.
As for their personalities, we’ve learned from reports that the siblings had rough childhoods and depended on each other for survival, giving them a different outlook on the world. Eventually these two will ditch the robot and join the Avengers, but it’s a good change of pace to see big-screen superheroes who aren’t heroes at the get-go. After fighting Earth’s Mightiest Heroes and giving them a run for their money, they’ll help stop Ultron from eliminating all life on Earth. While many of us don’t know what specifically awaits the twins within Avengers: Age of Ultron, Scarlet Witch is scheduled to return for Captain America: Civil War, though there’s no official word yet on what’s happening with Quicksilver.
U.S. audiences can see Quicksilver and Scarlet Witch when Avengers: Age of Ultron hits theaters on May 1.