Why it's good to be so bad

Mark Ruffalo remembers some of the comments posted when it was announced he would be playing The Hulk in Avengers Assemble. Among the kinder ones: Ruffalo is an idiot, the guy is barely awake, how's he going to be p***** off as The Hulk, bring back Ed Norton, etc.

"It was pretty brutal, it definitely hurt my feelings."

Next up is Chris Hemsworth, aka The Mighty Thor. Comments directed at him included: who is this guy, he's tiny, he did Dancing with the Stars and Thor doesn't dance, etc.

"It's the ridiculousness of it all," laughs Hemsworth. "They may as well have said, 'Oh, and he can't actually fly'."

Avengers Assemble is the first time these characters –Thor, Hulk, Black Widow, Iron Man, Captain America, Hawkeye – have appeared together in one film. The movie is also notable for being helmed by Joss Whedon, Buffy and Angel creator. For fanboys it rarely gets bigger than this.

The Hulk is the ultimate split personality in comic book land, part gentle Dr Bruce Banner, the rest the not-so-jolly green giant. Before he was famous for being cast as The Hulk, Ruffalo, the star of Zodiac, Shutter Island and The Kids are All Right, was known for being one of the most chilled actors in the business. Hard to imagine him having a temper.

"Ah, yes I do," he smiles. "It's just been wrestled and subdued." Selfishness brings it on, he says, greedy people and institutions (Ruffalo is a long-time environmentalist). And his kids, sometimes, he laughs. "If you're not yelling at your kids you're not spending enough time with them."

Courtesy of motion capture technology, the petite Ruffalo is the first actor to be able to play both Banner and The Hulk. For the motion capture scenes he had to wear a full body leotard covered with tiny camera points. It's not an outfit he remembers fondly. "It makes all the wrong places look big and all the right places look small."

As suggested by the internet chatter, he had a lot of expectations to live up to in playing The Hulk. "I've never had a performance so badly reviewed even before I shot a single frame. I didn't realise quite how scrutinised it was going to be until I was already in, otherwise I'm not sure I would have done it."

Paying tribute to earlier Banners, among them Eric Bana and Ed Norton, Ruffalo says Avengers Assemble picks up the story at a later stage.

"He's an older Banner now, he's been on the run longer, he's got to the point where he's tired of running and he has a certain sense of humour about himself and is turning to face the monster within him that he's been running away from."

In Avengers Assemble, he was alone among the superheroes in not having done his own film. Between that, and the earlier internet reaction, he felt like the new boy on the first day at school.

"I felt totally out of place, but I realised that everything I was feeling was pretty much really good for Banner. So I just took all my insecurities and all of that and just shoved it into the performance," he says.

"So," he laughs, "I want to thank those fans for being so hard on me."

Hemsworth had filmed Thor with Kenneth Branagh, but he also admits to a bout of the jitters coming on set with Robert Downey Jr, Samuel L Jackson, Scarlett Johansson and the rest. Like Ruffalo, he put the nerves and the internet numpties behind him. "The lesson out of all this stuff is you can't base your performance on the thousands of various opinions out there on who these characters are because they are all different anyway. You've got to own it."

Hemsworth, an Aussie, is soon to start playing a British sporting hero, racing driver James Hunt, in Rush. Directed by Ron Howard, the drama focuses in part on the rivalry between Niki Lauda and Hunt.

Hemsworth has become fascinated by the Formula One world of the 1970s With several drivers dying each season they all lived with the looming threat of death, he says. "That's a big roll of the dice." This bred different attitudes in different drivers. "Niki was much more intellectual and calculated about his approach whereas James was intuitive and more of a sort of artist in a way, head down, visceral, [taking an] animalistic kind of approach to driving and life."

He had to pile on the beef to play Thor, then shed almost two stones again to play Hunt. "When I put on the weight for Thor I was tired a lot. To lose the weight for Rush meant being underfed and over-trained. I was saying to my wife I had more symptoms of being a pregnant woman than she did – I was hungry and moody and tired."

Both Ruffalo and Hemsworth, as is the drill with franchises, are hoping Avengers Assemble does well enough at the box office to bring them together again. Contractually, Hemsworth is signed up for three Thors and three Avengers. Ruffalo has a six-film deal too. But as he says, if they put a Hulk out every three years he'd be well into his sixties by the end.

"I've a feeling they are going to get sick of me before I end up doing six pictures."

The financial security would at least allow him to get back to directing. After helming Sympathy for Delicious in 2010 he said he wanted to keep directing, yet there has been no time.

"It takes a lot longer to put together a movie than it does to get a part in one." He has, though, been working on a script in the interim.

Ruffalo isn't afraid to rearrange his life if needs must. At one point, he says, he was having to take jobs to pay for a house, cars, the rest of the bills. Then he dropped out for two years, devoting his time to his family– he has three children – and moving away from Los Angeles. It was, he says, a total restructuring of his life, and he's been much happier as a result.

"I just simplified everything and made it so if I want I could do one movie a year. The fact of just having that freedom all of a sudden reminded me of how happy I was just being an actor and how simple a life we could have and still be very happy."

Hemsworth and his wife, the actor Elsa Pataky, are about to have their first child. Between that, the recently released The Cabin in the Woods, Rush, and Avengers Assemble, it's a busy time. The baby, due soon, is his main focus now. "My biggest adventure of all. I can't wait."

Avengers Assemble opens today.