'Avengers: Age of Ultron': Here's all you need to know about the new characters

Getting confused by all the new faces popping up in clips from the upcoming 'Avengers' sequel? Here are some facts about each.

It was in the editing suite that "Avengers: Age of Ultron" writer and director Joss Whedon started to crack.

"There's like 47 of these people," he said of his large ensemble cast. "At some point during the editing process, I could not have told you who they were, who I was, what movie I was making. ... I got so lost in it."

For casual fans, movies in the Marvel Cinematic Universe can be particularly daunting with years of comics mythology informing every character and moment. Simplicity was not the goal with "Ultron," which adds even more people to the already massive group.

A quick who's who of some key newcomers:

THE ROBOT

James Spader wasn't familiar with the source material when he was approached to play Ultron, an 8-foot tall robot with designs to destroy the world in order to save it. Created for peace-keeping, Ultron is the perfect example of artificial intelligence gone awry. Whedon told Spader that he wanted the character to be three-dimensional and not just some killing machine. Recounting Whedon's directive, Spader said he was told that Ultron "has to be able to go from funny to frightening to childish because he is incredibly immature. He's like a powerful teenager. Underneath it all, he must always retain a powerful gravitas."

THE WITCH

Quicksilver and Scarlet Witch have a different backstory in the comics, but in "Ultron," Whedon explains their powers of speed and magic by making them products of human experimentation. After watching their parents die, the twins become set on revenge against those responsible. Elizabeth Olsen, who plays Wanda Maximoff/Scarlet Witch, watched Japanese horror films to prepare to play her skittish and creepy character, who can control minds as easily as she can create a fireball out of thin air. "I wanted to have gloves and things to protect her hands, because that's where her power was. It was like harnessing it," said Olsen.

THE RACER

As speedy Pietro Maximoff/Quicksilver, Aaron Taylor-Johnson said that his wardrobe was essential to creating his character. "Joss had the idea that he'd never be in the same pair of shoes twice. That he'd literally burn them out," said Taylor-Johnson, who also helped devise the detail that his character should be wearing clothes with reinforcements sewn in. "If he was running past trees or scuffing against walls at the speed he's going, he'd shed layers of skin and bone without the proper clothes." Working for Ultron against the Avengers, the twins create havoc in their ranks and prove formidable and quirky foes for the gods and superheroes.