Joss Whedon didn't know if he wanted to return for Avengers: Age of Ultron. The first film had left him completely exhausted, and — mentally and physically — he just didn't know if he had it in him to make a sequel. But, because he's Joss Whedon, he could not stop thinking of cool ideas for another Avengers movie. Chiefly, he had two things that were “absolutes” if he was going to return: Ultron and Quicksilver & Scarlet Witch.

Whedon explains his love for these two, affectionately referred to as “The Twins” saying, “They’re from my era, they’re very different, their powers are different. It’s not all punching, it gives a different palette. We can do more interesting things.”

Interesting indeed.

We presume you know all about Ultron by now. He's big and shiny and angry and hates the Avengers. But, what about Quicksilver and Scarlet Witch? In the trailers and posters we see them fighting alongside both Ultron and The Avengers. Are they good? Bad? Who are these guys?

The first thing Joss ever said to me before I even got the job was, ‘You will not have to wear a bathing suit or look like a porn star’ (laughs).

“It's not an easy answer,” admits Aaron Taylor-Johnson with a laugh.

Johnson is the British actor cast as Quicksilver, the second such iteration of the Marvel character in the past year (see: Evan Peters in X-Men: Days of Future Past). Elizabeth Olsen, an American, plays his twin sister, Wanda, aka Scarlet Witch. Both have to speak in an Eastern European accent.

“Me and Lizzy have been doing dialect coaching together and trying to get the sound similar to playing twins, brother and sister, especially her being American and me British.”

When we spoke to Olsen, she wouldn't say the name of the country the Twins are from (“That I can't talk about”), but can confirm it's the fictional country of Sokovia, the site of an underground Hydra compound, currently run by Baron von Strucker, the monocled villain seen at the end of the Captain America: The Winter Soldier credits.

“Strucker’s been doing experiments,” explains Whedon, “and he’s got [Loki's] scepter, and he’s been using alien tech on [Quicksilver and Scarlet Witch].”

Avengers 2 Scarlet Witch

The Twins are recruited from among a group of government protestors in Sokovia with the promise of more power. The government isn't going to protect you, so you need to protect yourselves. Strucker gives them that power. Almost all the subjects under his experiments die, except these two very “special” cases.

Scarlet Witch, who Whedon describes as “damaged” long before she became the subject of Hydra experiments, has powers unlike anything we've seen in the Marvel Cinematic Universe to date. It's, as Strucker announces in that post-credits scene, the start of the “Age of Miracles”.

“I am able to go into someone's head. I can feel and see what they feel and see, so it's not just me manipulating them, but for her everything that someone else could feel — their weakest moments — she physically goes through that same experience with them. If they have the biggest, darkest fear, I get to see that.”

They are powers you may have noticed in the trailer. Wanda entering the mind of Black Widow, or sending Hulk on a rampage in South Korea. This is, to put it mildly, a pretty big deal and part of why Whedon calls her “massively important” in Age of Ultron.

As significant as her mind control is, Wanda's powers don't stop there. “Also, I can control energy. I can manipulate energy away, so that's what the red stuff is that we're playing with.”

Avengers 2 Scarlet Witch

Because the Marvel Cinematic Universe has never seen a character quite like Wanda before, it took some practice and research to answer the question: How does this magic witch hero move?

Whedon had some initial ideas, mostly based on images he loved from the comics, but Olsen also worked extensively with choreographer and dancer Jenny Wade on her moves.

“So the two of us get locked up in a room together and we move and we try and figure out what looks strong and where the energy comes from. It's funny, because everyone's doing like stunt choreography, and she and I are just doing weird moves and shit, you know, pretending like we're making things shoot out of our hands (laughs).”

Then there's Quicksilver, Wanda's brother Pietro. Here's Johnson explaining his powers in the film:

“I run a lot.”

Haha, yes, very funny Aaron Taylor-Johnson. But, it's what Quicksilver can do with his speed that makes him a very big problem. Normally, it would take a character with the strength of The Hulk to drop Captain America, but as Johnson explains, his speed allows him to do some very incredible things.

“I go at such super speed that literally an elbow or an shoulder would send someone kind flying. It's the force of impact of my powers.”

Avengers 2 Quicksilver

Even though the movie versions of the characters have the names, powers and abilities of the comic book counterparts, not every aspect of the characters made it to the big screen. “The first thing Joss ever said to me before I even got the job was, ‘You will not have to wear a bathing suit or look like a porn star’ (laughs).”

Scarlet Witch's costume in the comics tended to be slightly more, uh, revealing. A tight leather corset, big red boots and a lot of décolletage. For the film, Marvel, Whedon and Olsen instead opted for a vibe that would instead reflect her dark personality; a long, black dress, leather wrist bands and a scarlet jacket.

Johnson says the look of their characters was designed to match their vagabond lifestyle. “They're sort of Eastern European travelers that are kind of picking out clothes as they go along.” Because of his powers, Pietro tends to favor “cycle tops and compression t-shirts” that allow a more free range of motion as he's moving faster than the speed of sound.

Vision Scarlet Witch

Costumes aren't the only thing longtime comic fans will be looking out for. Marvel readers will keep a close eye on Age of Ultron to see if there is any hint of the burgeoning romance between Vision and Scarlet Witch, two characters who were married and had a baby together in the books. But, if you're looking that deep into each of their storylines, you might be a little disappointed says Olsen. “They're both being introduced in this film, so...I think if you're like a big fan and you know what happens, maybe you'll start putting in your own interpretation on the things. But other than that, it's just, everyone's being created and born.”

It would be incredibly hard for any actor to join the Avengers movies at this stage; these actors have been working in this universe for years. For Olsen and Johnson, it helped that just prior to signing on to Age of Ultron, they had just wrapped filming on Godzilla (where, oddly enough, they played husband and wife).

“It was nice to know Aaron and nice to have a friend when you're joining such a big project like this with, um, potentially intimidating people.” Olsen cops to the fact that she was expecting some “diva stuff” from the myriad superstars in the cast, but says, “There's none of that at all on this set.”

While Johnson says he doesn't know exactly what their Marvel future has in store, he does seem to indicate that a spinoff movie isn't likely, but would jump at the chance to work with Olsen, and Marvel, again. “They'll probably sort of tag us into someone else's [movie], you know. It's a great studio to be a part of and I'm not just saying that cause it's the easiest thing to say. It becomes a really creative kind of family and a place where I enjoy working. It's important to have fun and work with good people, you know.”

Avengers: Age of Ultron opens in theaters on May 1.

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