LOS ANGELES (AP) -- Chris Evans could feel the power of "The Avengers" from the moment he stepped on set.
Reprising his role as Captain America, the 30-year-old actor joins Robert Downey Jr.'s Iron Man, Chris Hemsworth's Thor, Jeremy Renner's Hawkeye, Scarlett Johansson's Black Widow and Samuel L. Jackson's Nick Fury in the long-awaited Marvel superhero romp, in theaters May 4.
Just seeing his co-stars in their costumes was exciting, Evans said — especially on the first day of shooting with Downey and Hemsworth.
"I'd never seen either one of them before in their outfits. Obviously I loved the `Iron Man' movies and I had just seen `Thor' in the theater like a week prior, and I remember coming to set and seeing both of them suited up and just thinking, I think my initial thought was, `God, I wish I could work with those guys,'" he said. "And the immediate afterthought was, `(Expletive) I am! I am! I'm in a suit too! I can't believe this!' So that was a really nice geek moment for me."
Downey, who already starred in two blockbuster "Iron Man" films, was like the leader of the pack, Evans said, establishing a warm feeling on set that fostered camaraderie among the cast.
"He's the reason these movies are happening: If Iron Man had not done well, obviously we would not be doing these movies," he said. "He's like the matriarch. He's the dad. If he would have come to set with a different attitude or certain disposition, the fish could rot from the head down. I can't say enough about the guy. He's such an amazing man: His energy and his positivity and his friendliness and his charm, it just breeds allegiance, and as a result everyone just fell in line and it became a family right away, kind of thanks to him."
Evans is a superhero star in his own right. He debuted his character in last summer's "Captain America: The First Avenger," which took in more than $368 million. But he was happy to share the task of saving the planet with his fellow Avengers this time around.
"With this movie, it's such a load lifted coming to set going, `Look at all these Oscar nominees that I'm surrounded by,'" he said. "It's like a dream summer camp or something."
Not so dreamy was packing 20 pounds of muscle onto his naturally slender frame. Evans spent hours in the gym and hours more eating protein — a routine many of his co-stars followed to become superhero-size.
"It's such an uncomfortable feeling," said a slim and bearded Evans, looking nothing like his character during a recent tour to promote the film. "When you get that big, your bones start aching in the mornings. All of a sudden, none of your suits fit."
Before production begins on the next Captain America film, Evans is taking on roles far from the comic-book world. He recently finished shooting "The Iceman," in which he plays a hit man opposite Michael Shannon, Winona Ryder and James Franco. He was inspired to take the role because it's nothing like his Captain America character, which he played in two consecutive movies.
"It was like a year of playing this goody-two-shoes, and I just said man, I just want to go 180 degrees. I want to find the most polar opposite role I can find," he said. "This guy's it."
Next up for the actor is a film called "Snowpiercer," which he describes as "a pretty heavy drama with a sci-fi twist," starring Tilda Swinton, Ed Harris and Octavia Spencer.
In October, Evans will be back in the gym — and back on that high-protein diet — to prepare for his return to superhero status. The Captain America sequel starts shooting in January.
AP Entertainment Writer Sandy Cohen is on Twitter: www.twitter.com/APSandy.