Development

Avi Arad, the CEO of Marvel Studios, first announced plans to develop the film in April 2005, after Marvel Enterprises declared independence by allying with Merrill Lynch to produce a slate of films that would be distributed by Paramount Pictures.Marvel discussed their plans in a brief presentation to Wall Street analysts; the studio's intention was to release individual films for the main characters—to establish their identities and familiarize audiences with them—before merging the characters together in a crossover film. Screenwriter Zak Penn, who wrote The Incredible Hulk (2008), was hired by Marvel Studios to write the film in June 2007.
Casting began in October 2008 with Downey's signing. Though Don Cheadle was also reported to be reprising his Iron Man 2 role of War Machine for The Avengers, he later stated that he did not think the character would appear in the film. At the same time, two major prospects occurred for Marvel; Jon Favreau was brought in as an executive producer for the film, and the company signed a long-term lease with Raleigh Studios to produce three other big-budget films—Iron Man 2, Thor (2011), and Captain America: The First Avenger (2011)—at their Manhattan Beach.
In March, it was reported that Penn had completed the first draft of the script, and that Marvel editor-in-chief Joe Quesada and Avengers comic-book writer Brian Michael Bend is had received copies. Also in March, Chris Evans accepted an offer to play Captain America in three films including The Avengers. In April 2010, Variety reported that Joss Whedon was close to completing a deal to direct the film, and to rework Penn's script.