What do you get when you put Marvel's biggest superheroes in a room together? EW went to the set to find out

”Awwright, let’s get to work!”

Robert Downey Jr. struts onto the set of The Avengers wearing a gray bodysuit and boots and the bulky torso of his Iron Man armor. It’s too hard to move in the full outfit, so the robotic limbs are often added digitally later. In any case, he looks a bit like a cartoon character forced to wear a barrel after losing every stitch of clothing except his long johns, but that hasn’t dampened his confidence.

Downey strides over to Chris Hemsworth (who’s wearing royal-warrior regalia as Thor) and Chris Evans (who has the cowl of his Captain America outfit pulled back on his neck like a hoodie) and teases them like little brothers. ”May I see that?” he asks, reaching for Evans’ star-emblazoned shield. ”May I?” Evans hands it over, and Downey spins it slowly like he’s studying a record for scratches. He attaches it to his arm for a moment, striking a defensive pose, then flips it over like a bowl and turns to a prop master nearby: ”Put some nachos in that, would ya?” Downey hands the shield back to an amused Evans. He then gets down on one knee amid some rubble, like a man being knighted, as the costume crew attaches his battered gold faceplate and helmet.

The scene they’re prepping is part of The Avengers‘ climactic battle, an assault led by Thor’s villainous brother, Loki (Tom Hiddleston), who’s planning to make Earth his new kingdom after being expelled from their family’s celestial realm. Downey, Hemsworth, and Evans are standing among the battered cars, smoldering fires, and cratered asphalt of what is supposed to be a New York City bridge, but is really an abandoned train depot in the heart of Albuquerque, N.M., that’s serving as a makeshift soundstage. Loki has enlisted an otherworldly army to aid his conquest — something Marvel declines to confirm, though photos of extraterrestrial craft and weapons have leaked online, driving fans into a frenzied debate over which specific group of aliens from its vast comics history is causing the trouble.

For Avengers aficionados, there will be plenty of details to debate and drool over between now and May 4, 2012, when the film launches next summer’s movie season. But the lure of the film, particularly for casual fans, is simply seeing the buff and (mostly) brainy all-star team — Iron Man, Thor, Captain America, The Hulk, Hawkeye, and Black Widow — standing united at the law-enforcement agency S.H.I.E.L.D., which dispatches them in a giant flying helicarrier to danger zones around the world. Ironically, the actors tend to work only in small groups, shooting piecemeal, but the finished movie will feature a handful of sweeping battle shots of the gang in its entirety, fighting against impossible odds.

Loki, the troublemaker-in-chief here, was the villain in the Avengers’ first comic-book appearance 48 years ago, when writer-editor Stan Lee and the late artist/co-writer Jack Kirby teamed up some of Marvel’s most popular solo heroes in one place, just as rival DC Comics had done three years earlier with Batman, Superman, Wonder Woman, and others in the Justice League of America comics. The Avengers No. 1 was published on Sept. 1, 1963, and cost 12 cents.

The stakes are obviously much higher for the film, which just wrapped. At risk is not only its estimated $220 million budget, but also one of the most promising tentpole franchises in Hollywood. The Avengers comprises half a dozen iconic Marvel Comics characters, many of whom could spawn a stand-alone franchise (if they haven’t already). Iron Man 3 and Thor 2, each aiming for theaters in 2013, could be either dramatically helped or hurt based on how The Avengers is received. Black Widow and Hawkeye haven’t had solo films, though Scarlett Johansson and Jeremy Renner could be called into action if audiences react well. Meanwhile, legions of devoted fans worldwide are just praying The Avengers doesn’t get screwed up on its way to the screen. The movie’s writer-director, Joss Whedon, is one of them.

Sitting behind a bank of video screens, Whedon stares intensely at some frayed, handwritten notebook pages. The creator of Buffy the Vampire Slayer and the cowboy/space saga Firefly is a pop culture demigod — and no stranger to ensembles or superheroes, having helped with the script for this summer’s Captain America and having written some of the acclaimed Astonishing X-Men comic-book series. Still, The Avengers has him feeling like what The Hulk might call a ”puny human.” ”Every day I make some boneheaded mistake,” he confides. ”And I go, ‘Really? Wow. So no learning curve, huh?”’ Or maybe his superpower is the ability to spot mistakes no one else can see.

Other filmmakers have brought Iron Man, Thor, Captain America, and The Hulk to screens (with various levels of success), but The Avengers is something Marvel has been working toward since 2005, with the idea really taking hold when Samuel L. Jackson’s one-eyed spymaster Nick Fury showed up at the end of 2008’s Iron Man and said, ”You have become part of a bigger universe.”

Right now, that universe comes down to those crumpled pages in Whedon’s hand. He spent a year penning the script, but one of the luxuries — or curses — of pulling double duty on the film is the ability to rewrite obsessively. ”Peek behind the curtain,” Whedon says, showing off some scribbled dialogue. ”It was one line — now it’s three pages.”

In the sequence they’re about to shoot, Iron Man has just suffered a serious ass-kicking, and Thor and Captain America are coming to his rescue. When Thor rips Tony Stark’s helmet free, the unconscious billionaire was supposed to wake suddenly, catch his breath, and ask, ”What’s next?” Downey felt there should be more. Whedon agreed and put pen to paper, which resulted not just in a new series of exchanges between the three heroes, but a few alternates for Downey to say, giving the editors some options when it’s time to assemble the movie. One choice line from the bunch: ”What happened?” Stark groans, coming back to consciousness as Captain America and Thor loom over him. ”Please tell me nobody tried to kiss me.”

Evans raises another question as the cameras are about to roll. ”Wait, how do I check for a pulse?” he asks, realizing that Iron Man’s armor makes it impossible. Whedon’s face furrows as he thinks. Right. ”Press his chest, lean down, and feel for his breath,” the director says. Later, Mark Ruffalo shows up in the same scene as The Hulk, performing in a motion-capture suit he describes as ”a cross between a child’s pajamas, a test dummy, and a Chinese checkerboard.” He’s stomping in the background after catching Iron Man in his fall from the skies. ”Wait, I grabbed him in the air, saved him from hitting the ground, and now I’m just going to dump him?” he asks Whedon and co-producer Jeremy Latcham, who ponder the question, then nod. (The Hulk doesn’t do gentle.) Ruffalo laughs. ”Okay, you guys are cruel, though.”

Those were easy fixes. Others have been more taxing. Before filming began, Ruffalo had to take over the role of The Hulk from Edward Norton, who was dropped from The Avengers after clashing with Marvel over the final cut of 2008’s The Incredible Hulk. In the spirit of camaraderie, Ruffalo called his predecessor before accepting the role: ”Norton and I are friends, and he was like, ‘You’ve gotta do it, buddy.’ He basically bequeathed it to me. It was very cool and very generous of him.”

Once cameras are rolling, the only tension at all seems to come from script rewrites, like today’s. Whedon says he’s occasionally gone home after a long night of shooting and detoured straight to the local Starbucks (home office of all nomadic writers) to spend the dawn hours hammering out much more detailed new scenes. He laughs nervously. ”There is a weird element of: They handed me one of the biggest movies of all time, and I’m making it up as I go.”

That’s exactly how Downey prefers it. On the Iron Man movies, he became infamous for improvising and pushing for heat-of-the-moment script revisions. Or, as he colorfully puts it, ”I dominated like a rabid, horny gorilla.” But that impulse had to be tempered on The Avengers, which requires more sharing than he’s used to — something Downey learned after pushing too hard for Tony Stark to take center stage in Whedon’s early drafts. ”I said, ‘I don’t know what you’re thinking, but Tony needs to drive this thing,”’ Downey recalls, smoking a thin cigar during a break in filming. ”He was like, ‘Okay, let’s try that.’ We tried it and it didn’t work. Because this is a different sort of thing. Everybody is just an arm of the octopus.”

Downey says it was ultimately a relief to surrender leading-man status: ”They were able to figure it out so that not everybody is having their kidneys drained every day on the dance floor for the whole shoot, which is one way it could have gone.”

Banding together in real life comes with its share of challenges, though. Hemsworth actually feels more responsibility as part of an acting ensemble than he did as the solo lead in Thor. ”It ends up being a back-and-forth ball game between seven or eight people, instead of a two-hander, which is very intimate,” he says, stretching out in his trailer beside a stack of barbells he uses to keep Thor’s arms pumped during the shoot. ”You don’t want to drop the ball for the rest of the team.”

But in the end, the actors are so glad to be sharing the burden that the cast and crew joke that the code name for the movie — used to avoid unnecessary attention during the shoot — is Group Hug. ”Joss describes it as the definition of family,” says Marvel Studios president Kevin Feige, the sort of real-life Nick Fury who has spearheaded the Avengers project by way of the various solo superhero flicks. ”These are people who have no business being together, but they are thrust together and need to make the best of it.” To that end, he says Marvel is keeping the focus on these core characters, and not introducing a slate of new heroes through cameos. ”We didn’t want to make a big mess,” Feige says. ”They don’t walk through the S.H.I.E.L.D. commissary and see another 20 superheroes.”

As with every family, the Avengers tend to bicker. Expect at least one knock-down, drag-out brawl involving The Hulk after he gets uncontrollably angry. And it’s the personality clashes that fuel the movie: Downey’s Iron Man is cocky and reckless (he actually likes setting off The Hulk, to the dismay of his teammates); Hemsworth’s imperious Thor still struggles with tact around those he considers inferior (which is everyone); Evans’ Captain America, resuscitated after nearly seven decades, bitterly yearns for a lost time and long-gone loved ones; and Ruffalo’s Bruce Banner would rather be free of his mean, green alter ego than be used as an out-of-control weapon pointed in the direction of the bad guys. Add to that the longtime S.H.I.E.L.D. operatives Hawkeye (Renner) and Black Widow (Johansson), who are dubious about the unpredictable colleagues Jackson’s Nick Fury has brought to S.H.I.E.L.D.’s hovering headquarters. It manages to bring out the worst in the best of the best. ”Just because they’re superheroes doesn’t mean they’re superfriends,” says Renner. ”We all have our own cross to bear, and that becomes a big part of the movie.” The thing that binds them together is the same thing that tends to unite any troubled family: crisis. ”You almost get the feeling that none of us really want to be there, but we’re there because we have to be, because nobody else can do it,” Johansson says.

Ruffalo extends that point even further: ”Part of what’s cool about the story, and I think it’s a great metaphor for America, is there’s all these disparate people with their talents and ideologies. And in the end, in order to succeed, they have to band together. They have to put aside their egos and their own will for a greater good.”

One thing that helped the actors bond was shooting in New Mexico, where they all were out of their element. ”Any time you film somewhere where nobody is from, you’re forced to hang out together off set,” Evans says. ”No one knows anybody, no one has any prior obligations out here, no one has any dinner plans because we’re all alone.” Johansson, Ruffalo, and Renner caught a Mötley Crüe concert, and Whedon (when he’s not rewriting) has been known to take his team dancing. Wait…dancing? ”It’s my favorite thing in the world. I know every dance club in Albuquerque,” Whedon says, drop-dead earnest. ”It’s not like I’m deliberately saying, ‘Oh, we must foster a sense of unity,’ but it’s fun when you see everybody cutting loose together.” Renner says they got even closer when the production moved to Cleveland later in the summer: ”We were all in the same hotel, huddled together. It was like being at camp.”

Could they be getting along too well? Whedon shrugs. ”I was like, well, if they hate each other, I guess we can use that,” he jokes. ”But they don’t.”

Still, if you press him, Whedon will acknowledge a little on-set rivalry between the stars. ”If you spend the morning at the gym and you run into Chris Evans, and then he runs into Chris Hemsworth, and then he sees the Hulk model…” Whedon puffs out his cheeks and flexes his arms menacingly. ”I’m at the bottom of that. I’m at the part of the totem pole that you stick in the ground to keep the totem pole up.”

Maybe it just takes a different kind of strength to hold together a project like this. Somehow, he’s able to make it all seem like fun and games — and nobody even lost an eye.

Well…except for the Avengers’ eye-patch-wearing chief, Nick Fury. But blame that one on his own origin story.

Avengers 101
When Earth faces a supersize threat, the government agency S.H.I.E.L.D. — led by the eye-patch-wearing superspy Nick Fury (Samuel L. Jackson) — brings together a team of good guys known as the Avengers. Here’s a breakdown of who’s who.

Iron Man/Tony Stark
Robert Downey Jr.
The billionaire industrialist has a flying, rocket-firing suit of armor, and is kept alive by the same power source embedded in his chest that fuels his weaponry. But what really gets his motor running is being a smart-ass and a ladies’ man.

Captain America/Steve Rogers
Chris Evans
A scrawny guy with a big heart, Rogers was the lone success in a supersoldier experiment during World War II. Lost for generations after a crash landing in the Arctic, he has been revived only to find that everyone he once knew is gone.

Chris Hemsworth
This hammer-pounding prince from the celestial realm of Asgard views Earth as a day care for weaker beings but feels obliged to protect us from his villainous brother, Loki. Picture how you’d feel if your little brother picked bar fights with an entire planet.

The Hulk/Bruce Banner
Mark Ruffalo
Hit by gamma rays in a supersoldier experiment gone wrong, the mild-mannered scientist becomes a green monster when his temper flares. When the Avengers track him down, he’s reluctant to join, knowing his power can’t easily be controlled.

Hawkeye/Clint Barton
Jeremy Renner
Hawkeye doesn’t have mystical or scientific superpowers — he’s just really, really good with a bow and arrow. His natural skills as a sniper give him a working-class-hero attitude around his enhanced colleagues.

Black Widow/Natasha Romanoff
Scarlet Johansson
Another regular human, she’s a former Russian agent making amends for unspecified past wrongs. She’s the only female in the group, but nobody’s sweetheart.

What’s Next for Marvel?
Marvel Studios has spent the past seven years laboring over what they referred to internally as ”the big idea”: a long slate of interconnected movies culminating in next summer’s The Avengers. So what will keep them busy after that?

Iron Man 3
The movie is aiming for theaters in May 2013, with Kiss Kiss Bang Bang director Shane Black currently in preproduction.

Thor 2
Next April will mark the start date of the sequel, which will ”take Thor literally to other worlds,” says Marvel Studios president Kevin Feige. Director Patty Jenkins (Monster) is in talks for the job.

Still nebulous, but definitely in the works, is a film about the tiny hero with major strength being put together by Hot Fuzz writer-director Edgar Wright, who has ”developed an excellent draft recently,” according to Feige.

Guardians of the Galaxy
Says Feige, ”There’s an opportunity to do a big space epic, which Thor sort of hints at, in the cosmic side of the [Marvel] universe.” Begun in 1969, the comic focused on alien warriors who were each the last of his or her kind.

Another Marvel comic dating back to the ’60s, this one follows a society of heroes who evolved from alien experiments on primitive earthlings, and were then cast off into their own galactic kingdom. If either of these last two becomes a movie, Feige says, expect an X-Men-style ensemble, à la The Avengers.