Plot and Cast information from Wikipedia 

With S.H.I.E.L.D. destroyed and the Avengers needing a hiatus from stopping threats, Tony Stark attempts to jumpstart a dormant peacekeeping program with Ultron, a self-aware, self-teaching, artificial intelligence. However, his plan backfires when Ultron decides that humans are the main enemy and sets out to eradicate them from Earth, and it is up to Iron Man, Captain America, Thor, the Hulk, Black Widow and Hawkeye, along with support from Nick Fury and Maria Hill, to stop him from enacting his plans. Along the way, the Avengers encounter the powerful twins, Pietro and Wanda Maximoff, as well as the familiar Vision.

Cast

• Robert Downey, Jr. as Tony Stark / Iron Man:

The co-leader and benefactor of the Avengers,who is a self-described genius, billionaire, playboy, and philanthropist with electromechanical suits of armor of his own invention.

• Chris Evans as Steve Rogers / Captain America:

The co-leader of the Avengers, who is a World War II veteran enhanced to the peak of human physicality by an experimental serum and frozen in suspended animation before waking up in the modern world. Evans said that he was able to maintain the strength he built up for Captain America: The Winter Soldier by working out up to an hour a day. Evans said, “…you pull the plug about two to three weeks before you wrap. When you see the finish line coming, you are so glad to not have to think about the gym. But we are starting Avengers 2, so over the past month, I have been hitting it pretty hard.” Evans called Rogers “a soldier” adding, “he’s born into a world of orders and structure, and he likes being kind of a cog. So once S.H.I.E.L.D was kind of destroyed, he’s looking for structure. And now that the Avengers don’t really report to anyone, they report to each other, it’s a different dynamic for him and he’s trying to figure out where he fits in that.”

• Chris Hemsworth as Thor:

The crown prince of Asgard, based on the Norse mythological deity of the same name.

• Mark Ruffalo as Dr. Bruce Banner / The Hulk:

A genius scientist who, because of exposure to gamma radiation, transforms into a monster when enraged or agitated. Ruffalo worked with motion capture performer Andy Serkis‘ The Imaginarium Studios in preparation for the role. Ruffalo added, “[My role’s] even bigger than last time, and it’s more complex and it has more layers and a bit more arc. Not only that, but it seems that the motion capture process is becoming a whole lot more agreeable second time around. I’m really tripping on the technology of this motion-capture stuff… now I just completely embrace it and see it as this other exciting place we can go as performers.” Describing the relationship between Banner and Hulk in the film, Ruffalo said, “I think there’s a whole relationship with Banner and Hulk that needs to be discovered. There’s a very cool thing happening: Hulk is as afraid of Banner as Banner is afraid of Hulk.” Ruffalo added, “Both of these guys are obviously the same guy, and they have got to come to peace somehow with each other. And I think that this confrontation is building along the lines of this film.”

• Scarlett Johansson as Natasha Romanoff / Black Widow:

A highly trained spy, formerly of S.H.I.E.L.D. Producer Kevin Feige stated that more of the character’s backstory is explored in the film. Johansson elaborated, “In Avengers 2 we go back… we definitely learn more about Widow’s backstory, and we get to find out how she became the person you see. All of these characters have deep, dark pasts, and I think that the past catches up to some of us a little bit.” On where the film picks up Widow’s story, Johansson said, “At this stage, when you see the Widow, she’s — especially in Avengers, these characters all have a past, and hers is a very complex one, where she’s realizing — and it’s kind of a continuation of Cap 2 — ‘I’ve never made an active choice. I’m a product of other people’s imposition.’ That’s going to catch up with her. That’s bound to have a huge effect. There’s got to be a result of that realization… You’ll see her actively making some choices in her life, for better or worse.” A mixture of close-ups, concealing costumes, stunt doubles and visual effects were used to help hide Johansson’s pregnancy during filming.

• Jeremy Renner as Clint Barton / Hawkeye:

A master archer who previously worked as an agent for S.H.I.E.L.D.Whedon said that Hawkeye would interact more with the other characters in the film, as opposed to the first film where the character had been “possessed pretty early by a bad guy and had to walk around all scowly.”

• Samuel L. Jackson as Nick Fury:

The former director of S.H.I.E.L.D. who originally recruited the Avengers. Jackson described the role as a cameo, saying, “I’m just kind of passing by… Because, it’s another one of those ‘people who have powers fighting people who have powers’. That’s why I didn’t get to New York in The Avengers. There’s not a lot I could do except shoot a gun.”

• Cobie Smulders as Maria Hill:

A former high-ranking S.H.I.E.L.D. agent who now works for Stark.^[25][26][27] Describing Hill’s situation in the film, Smulders said, “I think, you know, after [Captain America: The Winter Soldier]…you’re sort of left a bit shell shocked, and I think we’re coming into this movie where we don’t really know who’s a good guy and who’s a bad guy and she’s trying to figure out that throughout this film.” She added, “She’s not getting any sleep. She’s doing all the work. She doesn’t have the kind of manpower that she had in S.H.I.E.L.D.”

• James Spader as Ultron:

An artificial intelligence programmed with elements of Tony Stark’s personality, who is overwhelmed with a god complex and desires to bring peace to Earth by eradicating humanity. Director Joss Whedon stated that Spader was his “first and only choice” for the role, because of his “hypnotic voice that can be eerily calm and compelling” while also being very human and humorous. Feige clarified, “We’ll be capturing his face and his body to create a whole performance… We did not hire James Spader to do a robot voice.” Extensive scans were taken of Spader’s head and body in preparation for the role. About the character Whedon said, “He’s always trying to destroy the Avengers, goddamn it, he’s got a bee in his bonnet. He’s not a happy guy, which means he’s an interesting guy. He’s got pain. And the way that manifests is not going to be standard robot stuff.”Whedon added that Ultron is “not a creature of logic – he’s a robot who’s genuinely disturbed. We’re finding out what makes him menacing and at the same time endearing and funny and strange and unexpected, and everything a robot never is.” Whedon also indicated that some of Ultron’s abilities from the comics would be stripped. Spader called the character “self-absorbed” said, “I think he sees the Avengers as being part of a problem, a more comprehensive problem in the world. He sees the world from a very strange, [biblical] point of view because he’s brand new, he’s very young… He’s immature, and yet has knowledge of comprehensive, broad history and precedent, and he has created in a very short period of time a rather skewed worldview.”

• Elizabeth Olsen as Wanda Maximoff / Scarlet Witch:

The twin sister of Quicksilver, who can harness magic and engage in hypnosis and telekinesis.Olsen said, “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. 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.”Olsen drew on her relationship with her older brother and her twin sisters to prepare for the role.

• Aaron Taylor-Johnson as Pietro Maximoff / Quicksilver:

The twin brother of the Scarlet Witch, who can move at superhuman speed.About the character Taylor-Johnson said, “Him [sic] and his sister [Scarlet Witch] have been abandoned by their parents and their father, and they grew up in Eastern Europe defending and looking out for themselves and each other… His sister really is his guidance – emotionally she’s the one who looks after him, and vice versa. He’s very overprotective physically – he doesn’t want anyone touching her.” Taylor-Johnson also said that Quicksilver has “real anger frustration” and is easily bored due to a short attention span.Feige stated exploring Quicksilver’s relationship with his sister and his backstory growing up in Eastern Europe would help differentiate the character from Evan Peters‘ version in X-Men: Days of Future Past (2014).

• Paul Bettany as Vision:

Bettany, who voiced J.A.R.V.I.S. in previous films,said, “I got a call on a Friday night from Joss going ‘Do you want to be the Vision?’ I can’t explain the amount of luck that went into that. And frankly for ages, because I understood once you were one character in a Marvel series and never another, I understood that was my thing. I’d be J.A.R.V.I.S. and get my bag of cash and go.” On what intrigued him about the role, Bettany said, “The thing that appealed to me is that this sort of nascent creature being born, being both omnipotent and totally naive, the sort of danger of that and complex nature of a thing being born that is that powerful and that created in a second and the choices he makes morally are really complex and interesting. They’ve really managed to maintain all of that”. Bettany also stated that the Vision feels paternal and protective to a number of people in the film, particularly Scarlet Witch, and has the ability to change his density. Bettany did wire work for the part.

Additionally, Don Cheadle, Hayley Atwell, Thomas Kretschmann,and Stellan Skarsgård reprise their roles from previous MCU films as Col. James “Rhodey” Rhodes, Peggy Carter, Baron Wolfgang von Strucker, and Erik Selvigrespectively. Claudia Kim was cast as a doctor/scientist and friend of Tony Stark. Andy Serkis is playing an undisclosed role in the film. Avengers co-creator Stan Lee will make a cameo appearance.