The superhero film produced by Marvel Studios also stars Chris Hemsworth, Mark Ruffalo, Chris Evans and Scarlett Johansson among others.
Before the reel, the cast of the 'Avengers' was brought out, teasingly, one at a time to music, starting with Downey, who threw roses into the audience, said The Hollywood Reporter.
"I become a little less significant every time," Downey said, referring to the growing cast of the franchise.
"You're the best, Robert!" shouted a fan, to which Downey jokingly replied, "You're probably right."
The film was announced in May 2012, after the successful release of 'The Avengers'. It is expected to release on May 1, 2015 in North America.