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Jay Maidment, AP
This photo provided by Disney/Marvel shows, Chris Evans, left, as Captain America/Steve Rogers, and Chris Hemsworth as Thor, in the new film, "Avengers: Age Of Ultron." The movie releases in U.S. theaters on May 1, 2015.

Prior to the May 2008 release of "Iron Man" — the movie that kicked off Marvel's ongoing rule of the box office — you can hear the uncertainty in director Jon Favreau's voice.

"Marvel doesn't have its own (movie) lot yet; maybe someday they will," he says.

The work on the first film could roll over to a series of films, "if we could be so lucky," he states later.

"I really don't know how people are going to react to this thing," he concludes. "I know the people close to me seem to like it... I don't know."

Years later, the series of films Favreau hesitantly hoped for in 2008 have come to pass not only with Iron Man, but other Marvel characters as well, and the Marvel juggernaut keeps rolling forward.

In celebration of the new film, "Avengers: Age of Ultron," here's a behind-the-scenes look at 50 things you might not know about the previous 10 Marvel movies