Avengers assemble on the big screen

Comic book fans finally get the chance to see their favourite heroes together when Avengers Assemble - several years in the making - arrives on the big screen this weekend.

"Avengers is going to do big business, that's in the cards," a confident Robert Downey Jr says. "But it deserves to succeed because it was a difficult endeavour and there's a lot of talent in it."

How difficult can it be to get Iron Man, The Incredible Hulk, Thor, Captain America, Hawkeye and Black Widow in one film?

Very, it turns out.

The idea for uniting some of Marvel's biggest superheroes on screen first emerged during early production of Downey Jr's blockbuster, Iron Man, in 2008.

Samuel L Jackson's character, Nick Fury, first appeared in Iron Man in 2008

Producer and president of Marvel Studios Kevin Feige discovered that the characters which hadn't already been brought to the big screen by other Hollywood studios happened to come from the comic book series The Avengers, first published in 1963.

Deciding to test the water to see whether there would be demand for an Avengers movie, producers slipped in an end-of-credits scene with Samuel L Jackson as Nick Fury, the director of fictional peacekeeping agency Shield, to gauge fan reaction.

The buzz was positive and after Downey Jr made a cameo at the end of The Incredible Hulk a couple of months later, Marvel decided to pursue an Avengers film by building it one character at a time - and so came blockbuster hits Thor and Captain America last year.

Downey Jr says all the films were inextricably linked: "All the franchises we've launched so far had to work - and if this didn't work out it would have affected all the other franchises."

Logistics

After ensuring all the previous films' writers and directors were on board with working towards an Avengers film came the task of creating a story to unite the characters and make a movie to trump all that had come before it.

Buffy the Vampire Slayer creator Joss Whedon took up the task of writing and directing the project.

Scarlett Johansson reprises her role as Black Widow while Jeremy Renner stars as Hawkeye

The film sees Fury assemble the special team in order to rescue the world from Loki (the villain from Thor, played by British actor Tom Hiddleston) and an alien army who plan to enslave the human race.

"Part of making this movie is taking everything that existed in the movies we've already put together and to then go back to the comics and be faithful to those," Feige says.

And when you have so many A-listers in the same film - Jackson, Downey Jr, Scarlett Johansson and Mark Ruffalo to name a few - getting them to be available at the same time can prove another challenge.

Consequently, there were not many days when the entire cast were on set during its three-month shoot.

"It was hard to have perspective of the size of the film as we were all almost making our own mini-films with so many storylines going on," Johansson says.

"The only time we got a real sense of the scope of it was when we were all together shooting the scenes in one unit - then there was an electricity in the air."

Creating The Hulk

Johansson reprises her role as former Russian spy Natasha Romanoff, also known as Black Widow, who was first seen opposite Downey Jr in Iron Man 2.

With a more fleshed-out role in this film, the star hints that if her character is well received, there could be the possibility of starring in more movies - maybe even her own franchise.

"Marvel understands the value of fan participation and if the fans respond to certain characters, they'll invest more in that character," she says.

"There's always the possibility [of more films], but even if there was a possibility, we'd never tell."

One newcomer to the franchise was Ruffalo, who plays Bruce Banner and The Hulk - roles played by Edward Norton and Eric Bana in previous films.

A Hulk fan as a child, Ruffalo says he was attracted to the idea of being the first actor to play both roles, as the giant green monster had been only a computer-generated creation before, and this time motion-capture technology would be used.

"People have had a great expectation of the Hulk for a long time," he says. "But technology has advanced to the point where an actor can inhabit the Hulk and there's now a seamlessness between Banner turning into him."

Ruffalo adds his experience has made him more sympathetic to the issue of more recognition for motion-capture actors during awards season, raised when Lord of the Rings actor Andy Serkis was overlooked for his performance as Gollum, and highlighted again with the stars of James Cameron's Avatar.

Mark Ruffalo is the first actor to play both Bruce Banner and The Hulk

"There's a performance, but there's also the aspect of the animators too which rarely gets talked about," he says.

"It would be cool if the whole team was considered, [but actors] should at least be recognised or have the capability of being recognised in some way.

"Yes there was an element of wearing a leotard, but it was a very intensive process."

Egos

Despite the A-list ensemble, the cast insist there was no room for individual egos on set.

"Once we realised the trailers were the same size we calmed down," Ruffalo jokes.

Hiddleston adds: "It would be so ironic trying to make a film about the achievements of a team to have a load of individuals throwing their toys out of their prams and acting like divas."

And being superheroes, the cast had moments of "wardrobe embarrassment" which led them all to be humiliated at one point or another.

"My leotard made all the wrong places look big and all the right places look small," Ruffalo complains.

Hiddleston adds: "Chris Evans and Scarlett were flying the flag for Spandex - and there was a moment when I saw [Thor] Chris Hemsworth being literally drilled into his costume as one of the discs on his breastplate had fallen off."

Reviews so far have been largely positive, but the litmus test is whether fans of the comic book series approve. They will be the ones whose reaction decides whether the Avengers franchise continues.

Nevertheless, the cast are prepared to be tied to the series - and everything else that comes with it.

"We don't know what the future holds for these characters - we all signed on with the hope that we'd be able to explore them more," Johansson says.

"But I love the action figures - I just became Lego which is the best thing that ever happened to me."

Avengers Assemble is on general release now.