Though Marvel Studios President of Production Kevin Feige recently said The Avengers is devoid of the little hidden references commonly known as "easter eggs" that have populated previous studio releases — "I find that they're distracting. Joss [Whedon, writer-director] finds that they're distracting. Frankly we want Avengers to work as its own movie, as a part one." — there is at least one hidden "cameo" to be found.
In a new featurette titled "The Sound of The Avengers, sound editor Christopher Boyes (King Kong, 2005) explains the effects behind everything from Thor's (Chris Hemsworth) hammer to Cap's (Chris Evans) shield to the Black Widow's (Scarlett Johansson) karate kicks. He also reveals that TV Hulk Lou Ferrigno contributed to the voice of the Hulk in The Avengers. watch the featurette >>