Ever since it was first revealed that Loki wouldn't be the only adversary facing Iron Man, Thor, Captain America, Hulk and the other Marvel heroes in "The Avengers," fans have been assuming that the trailer's alien attackers were Marvel Comics mainstays The Skrulls. Director Joss Whedon denied it, without giving any real answers...until now. 

Whedon finally clarified a little more about the extraterrestrial villains at a recent press conference.

"The alien race is the Chitauri, or a version of them," the director revealed, "because they're not one of the key races in the story and history. That wasn't the point."

The Chitauri have appeared in several Marvel Comics stories, including a WWII-era run-in with Captain America, and a more recent battle with heroes in "The Ultimates." The shape-shifting beings are, naturally, hellbent on conquering the planet. Maybe The Skrulls will pop up in later films.

Whedon also touched on the reasons why the film includes cameos from some Marvel movie vets (Gwyneth Paltrow's Pepper Potts), but not others (for example, Hulk's love interest Betty Ross).

"We separated the characters from their support systems in order to create the situation for a team," he explained." And also so when they go back to their own movies it has something that "The Avengers" doesn't have. But Pepper was really Robert (Downey Jr.)'s thing. He didn't want to be crazy-alone guy, he wanted to be crazy-in-a-relationship guy. He really thought Gwyneth would bring something great to the table and we really thought so as well. He's the one who convinced her to come do it. That made sense because he's been through two movies, he's had more of a journey, he's in more of a stable place."

"The Avengers" opens May 4.