Iron Man teams up with China's Dr Wu

The film's Chinese elements also include product placement by TCL, China's leading television and mobile phone manufacturer.

Iron Man 3 is not the only Hollywood film to have Chinese connections.

Paramount's Transformers 4 will be partly filmed in China and star Chinese actors. Brad Pitt's World War Z, to be released in June, has also been tinkered with to make it more Chinese-friendly. The source of a plague in the film is China in the Western version, but in the Chinese version, the virus is called Moscow flu.

"The attractive Chinese market is the reason, no doubt of that," says Ben Ji, a senior producer who has worked in both Hollywood and China. "Probably, there will be more Chinese-friendly versions for Hollywood tent-pole films, but these special versions do not enhance the films' quality. I don't see it becoming a mainstream approach. It is more like a special marketing approach in a certain period."

According to the Motion Picture Association of America, China replaced Japan in 2012 as the second largest film market in the world, next only to the United States.

China's box office has been surging by up to 30 percent a year since 2003. It has been the biggest overseas box office territory for many Hollywood films, such as Kung Fu Panda 2 and Avatar.

The Chinese government has loosened controls on imported films, allowing 14 more foreign films, in 3D or IMAX, to be released in theaters every year.

The first two Iron Man films were released in China. Iron Man was the fourth highest grossing foreign film in China in 2008 and Iron Man 2 the sixth in 2010. Disney is confident it can reprise the glory with its latest installment.

"We are confident that our stories will continue to be enjoyed by Chinese audiences," the company says. "And adding a local flavor will enhance the appeal and relevance of our characters in China's fast-growing film marketplace."

But the market is not just a field of gold. With the existence of censorship and the absence of a rating system, Hollywood studios face complicated challenges.

For example, Quentin Tarantino's revenge drama Django Unchained was pulled from theaters on Thursday, it's opening day in China, for what authorities defined as "technical reasons". The release date is still unknown.

Iron Man 3 will premiere on May 3 in the United States and China.

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