It's no surprise that Marvel's 'Avengers: Age of Ultron' might very well be the most difficult and intricate film project the franchise has developed as of yet, but a recent interview with director Joss Whedon informs us that some cast members had a more difficult time with it than others.

Whedon sat down with Marvel to discuss James Spader's "nightmare" experience in filming for Ultron. The experienced actor plays the voice and motion capture for the titular villain.

He starts off by doing an impression of the 'Blacklist' actor saying, "He has that voice, that very terrifying 'I own everything' maleficent evil voice and then suddenly get very peevish about something. He can go from very intense to very comedic, and get there on a dime beautifully."

Classically, in the comics, Ultron's face isn't expressive as he is essentially a robot, but the movie gives some leeway on the villain to bring him to life. All of Ultron's face motions in the movie were pulled from Spader's motion capture performance. The problem arose for Spader through the gear and set up for the mo-cap.

"It was a nightmare for poor James because he wears glasses, which he could not wear," Whedon explained. "And he was wearing a helmet with two cameras with light on them shining into his eyes and he has to go around set like he is an eight foot robot quickly and confidently over these jagged sets."

What has been shown in the trailers so far are very impressive so it appears that Spader took the experience as a champ. Whedon gave the actor his credit at the end stating that he just "went for it."