In an interview with MTV Tony Stark himself, Robert Downy Jr, has spoken of the difficulties in getting the tone for the Avengers movie right. “The danger you run with colliding all these worlds is that Jon [Favreau] was very certain that Iron Man should be set in a very realistic world. Nothing that happened in Iron Man is really outside the realm of possibility,” Downey Jr says. “Once you start talking about Valhalla and supersized super soldiers and jolly green giants it warrants much further discussion.”
There are inherent difficulties in bringing together so many characters in the one movie, but with the right approach, the right tone and, most importantly, the right script they should be navigable.
Downey Jr is signed on for Iron Man 2, which Favreau is directing, as well as for the Avengers movie, due in 2011, which Favreau is executive producing.