Johansson said Whedon confided in her that "'This movie is impossible. ... This movie, it can't happen. These characters don't belong in the same universe.' laid it out, said, 'It was an impossible feat. And so now we have to overcome it.'"
Part of the challenge was creating a story that would give equal treatment to six superheroes AND to the actors who portray them, such as Robert Downey Jr, who played "Iron Man" in two hit films. "He is Iron Man now," said Blackstone.
"Yes, he really is. I mean, even to the point where I believe he has sort of bled back into the comics," said Whedon. "From the very start, they said, 'Robert is a force to be reckoned with.'"
The writer-director said his star would come up with his own lines. "I would throw him things on the day," Whedon said, "I'd just give him a word, and he would just take that word and run with it.
"And I'm going to take credit for all of it!"
But Whedon is likely to get the blame, if it turns out "The Avengers" is not one of the biggest movies of the summer.
"Believe me, people are like, 'Oh, this is big, don't mess it up! Oh, we need to make this amount of money!'" Whedon said. "And I'm like, 'This amount of money exists? Whoa!'"
Early reviews suggest "The Avengers" is entertaining enough it could well make that amount of money. Still, Whedon's next movie is decidedly small scale: Shakespeare's "Much Ado About Nothing," which Whedon shot entirely at his Santa Monica home.
But Whedon, who has been happily practicing "small and quirky" for years, may soon be - like "The Avengers" themselves - hailed as a Hollywood superhero.
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