An unforgiving artificial intelligence program gets top billing in Avengers: Age of Ultron, but there will be plenty of pain caused by a pair of twins and a being known as a “synthezoid,” too.

Among the new characters in next May’s superhero team-up are Quicksilver, the Scarlet Witch and the synthetic humanoid creation known as The Vision. The trio has been a long part of Avengers comic-book history, though their allegiance is always questionable.

This time around, there’s no doubt: they’re troublemakers—although you can’t rule out salvation for them.

“They’re on Team Ultron, which makes things really hard for the Avengers because all of sudden they’re dealing with powers that they’re not used to,” says director Joss Whedon.

Aaron Taylor-Johnson and Elizabeth Olsen play Quicksilver and Scarlet Witch, a brother who can move at lightning speed, and a sister who can harness magic and engage in hypnosis and telekinesis.

“With the [first] Avengers, everybody pretty much had the power of being able to punch somebody,” Whedon says. “And now we have a woman who can get inside your head and move objects, and a boy that can move faster than anything, and a robot [Ultron] who can self-replicate and is out of his mind. So all of sudden, it’s a darker, weirder, tougher world that they’re living in.”

If it’s deja-vu all over again for Marvel fans, that’s because Quicksilver also turned up in the recent X-Men: Days of Future Past, played by Evan Peters. The character is the same, but the backstory is different. For one, no mention is made in Avengers of Magneto (the twins’ father) or their “mutant” abilities, which are part of the comic-book company’s X-Men licensing deal to Fox. In the midst of filming, Taylor-Johnson said he hadn’t yet seen the latest X-Men, but wanted to. “There’s no rivalry at all,” he says. “I’ll see it, but not see it from the standpoint of going ‘I’ve gotta do it better than that,’ or to do it differently in any way. What we’re doing is from another standpoint.”

BROTHER BREAKS BAD

In this Marvel universe, Quicksilver and Scarlet Witch are cast-offs from Eastern Europe, battle-scarred, and alone. So Taylor-Johnson has been working on his accent as well as his running skills. “They’re gypsies in a way. They’re romani. They’re sort of like travelers,” the actor says. With no ties to the world, naturally they couldn’t care less if it burns.

The core of this version of Quicksilver is his short fuse. “There’s a lot of clashing. He’s quick tempered. He gets agitated. He’s impatient. But he’s super protective,” Taylor-Johnson says. The one thing he does care about: his sister. “They’re very yin-and-yang in that twin sense. In his power, he’s physical and she’s psychological. My character is very much on the frontline, but he can be quite emotional. You see this beautiful tenderness between them.”

The two are orphans, who harbor a secret grudge against the Avengers. Their lack of family and any other connection to the world fuels their rage. As Whedon puts it, “I’m interested because there’s familial issues with that kind of resentment. You can sort of go deeper and I can play with their relationships and I can play with attitudes. Scarlet Witch and Quicksilver hate them with a fiery hate…”

They aren’t just brother and sister, they are—in a way—parents to each other, too. At least symbolically.

“When you look in the comic books, you see a lot of the time that she’s always sort of mothering him,” Taylor-Johnson says. “He’s like the father figure and she’s like the mother figure. Emotionally, she can stabilize him, and he protects her physically, vice-versa. So they have this beautiful connection and it’s kind of them against the world.”

TWISTED SISTER

The Scarlet Witch is always in an eerie, otherworldly state—overwhelmed by the vast psychic knowledge inundating her at all times. “The reason she’s so special is because she has such a vast amount of knowledge that she’s unable to learn how to control it,” Olsen says. “No one taught her how to control it properly. So it gets the best of her. It’s not that she’s mentally insane, it’s just that she’s just overly stimulated. And she can connect to this world and parallel worlds at the same time, and parallel times.”

The actress said she drew on her own family experience—having a very close relationship with her older brother, and witnessing first-hand the interaction of twins. (She’s the younger sister of former child stars Mary-Kate and Ashley Olsen.)

“My understanding of twins is that they always balance each other out,” she says. “When one’s high, the other one’s low. When one’s sick, the other one’s healthy. That happens, I think, a lot more often than not when people are really close as twins.”

Olsen and Taylor-Johnson were last seen together as a romantic couple in this summer’s Godzilla remake, and there’s a hint of uncomfortable closeness between the brother and sister. It’s a mainstream action film, so don’t expect any major taboos to be broken. But… there may be creepy little allusions.

“In the comics, every time you see an image of them, they’re always holding each other’s hand and looking over each other’s shoulder,” Olsen says. “They’re always so close, it’s almost uncomfortable. Aaron and I have been playing a little bit with those kinds of images just for ourselves.”

In the comic books, one character Scarlet Witch does strike up an overt romantic relationship with is The Vision, a synthetic, superpowered human designed by Ultron to show he has the power to create life, too. (Did we mention Ultron has major daddy issues?)

SYNTHETIC SOUL

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Vision will be portrayed by Paul Bettany, who has already been a part of the Marvel movie universe as J.A.R.V.I.S., the Siri-like artificial intelligence who serves as Tony Stark’s laboratory sidekick.

Ever since his casting was revealed, fans have been wondering: Coincidence… or can we assume Ultron uses J.A.R.V.I.S.’s consciousness for spare parts in his Vision-ary experiment? Whedon takes a deep breath. We’re in spoiler territory. “It’s not coincidence,” is all he reveals. “And I’m not going to tell you any more about The Vision.”

Downey wasn’t as cautious: “Things only happen arbitrarily in Kevin Feige’s Marvel universe by mistake, and I think he’s maybe made two mistakes and they weren’t really in the movies. They were more in like the easter eggs early on. Things that he didn’t have as much final say over but would nowadays.”

So, to be clear, it’s not just some accident that the voice of J.A.R.V.I.S. is now playing The Vision?

“Yeah, I don’t think Kevin would let that happen,” Downey says. “Again, it’s like if you think about the five different ways that [The Vision] could come together, this one’s definitely the most interesting of the five. I was running other scenarios and I’ve seen it progress over drafts. It was just kind of really good, right from the start.”

Marvel didn’t release any images of Bettany in costume as The Vision, but EW saw test footage of his make-up while on the set of the movie last month. While his face seemed to be a little more on the purple side of the spectrum than orange, the overall look of the synthezoid has a slightly more technological edge than the original 1968 introduction. He’s a bit more Borg and a little less Crayola.

But for the first time, Bettany will be turning up on screen in a Marvel film—instead of just supplying a voice. “By his own admission, he’s very disappointed that he actually has to show up this time,” Downey says.