In Phase 1 of the Marvel Cinematic Universe, the origin story for Thor helped setup the villain and main plot of The Avengers. A key to the pseudo-science involved in making the otherworldly stuff in Thor and The Avengers work was the character of Dr. Erik Selvig played by Stellan Skarsgård, a mentor of Natalie Portman’s Jane Foster. Selvig returned again in an even wackier, comedic exposition-focused role for Thor: The Dark World for even more questionable science-y plot necessities and we just learned that he’ll be back again for The Avengers: Age of Ultron.
From what we know about The Avengers sequel, it’s very Earth-based. The titular villain Ultron is a creation of hero Tony Stark (Robert Downey Jr.) and new potential hero Vision is a creation of Ultron. There are no alien armies, portals opening over major cities or flying space whales involved… that we know of. Yet in chatting with Total Film, Skarsgård confirmed that he does have a part to play in writer and director’s Joss Whedon’s sequel to The Avengers and that he’ll again be there to serve a very specific purpose.

After joking in the interview about how he first joined Marvel and had little faith or knowledge that a superhero franchise could become what it is today, Skarsgard explained that he has the number of Marvel Studios president of production Kevin Feige’s and can call him whenever he has “a problem with the scene.” He continues, “you can’t do that when you work on a normal Disney film or with Warner Bros or Paramount.” That would be terrible for a director if every actor could go over their head but the actor confirmed that he signed on for five films before revealing that he has “a small appearance” in Age of Ultron in what he describes as “something really nice.”“Yeah, I was naked again. They called my agent and said, ‘Do you think Stellan will mind being naked?’ My agent laughed his head off. Yeah, I almost insist! Sometimes with a contract you get a nudity clause, which is fantastic. It’s supposed to protect me from having my genitals exploited, which I doubt anybody would make a dime on.”

“First of all, I don’t know what I’m allowed to say. But usually they call me in if they need something explained. There’s a lot of explanations to do when it comes to that universe.”If we’re getting naked older Skarsgård again (and not his son who’s frequently naked in HBO’s True Blood), we could be seeing another scene of Selvig losing his mind again just like we saw in Thor: The Dark World. That or Whedon is simply playing on that naked gag for laughs. We expect it to be the former if he’s there to explain stuff and maybe Selvig is one of the many cameos we could see during the widely reported party scene at Avengers tower that was partially shown in the San Diego Comic-Con footage.

We know the film picks up from the post-credits button scene of Captain America: The Winter Soldier where new villainous character Baron von Strucker (Thomas Kretschmann) is experimenting on Loki’s staff and Chitauri alien technology from The Avengers and seemingly using it on other new characters, the twins Quicksilver (Aaron Taylor-Johnson) and Scarlet Witch (Elizabeth Olsen). Perhaps Selvig’s expertise comes in handy with The Avengers learning how the newcomers have powers or in deciphering what Strucker has been up to. Maybe Ultron seeks Selvig out for knowledge?If Stellan Skarsgard does have five-picture contract though, it’s a safe bet he’s back for Thor 3 which is currently without a release date but has a script in the works by Craig Kyle (Thor: Tales of Asgard) and Christopher Yost (Thor: The Dark World). Ready for more naked Selvig?The Avengers: Age of Ultron releases on May 1, 2015, Ant-Man on July 17, 2015, Captain America 3 on May 6 2016, and unannounced films for July 8 2016 and May 5 2017, Guardians of the Galaxy 2 on July 28 2017, November 3 2017, May 4 2018, July 6 2018, November 2 2018 and May 3 2019.

http://screenrant.com/the-avengers-2-stellan-skarsgard/