Known for TV shows with cult followings, Joss Whedon would only get involved in "Marvel's The Avengers" if he had a script he believed in. Unfortunately, that meant trashing the draft by Zak Penn that Disney was sitting on.

Whedon was brought into the project at a late date, as recounted in "Joss Whedon: The Biography" by Amy Pascale, which comes out on August 1. It was during an initial interview with Kevin Feige, president of production at Marvel Studios, that he saw Penn's script and passed judgment.

"I don't think you have anything," Whedon told Feige. “You need to pretend this draft never happened.”

"There was a script," Whedon acknowledged in a later interview with GQ. "There just wasn't a script I was going to film a word of."

Feige and company may have been displeased to hear this, but people took Whedon seriously. After all, he was the genius behind "Buffy the Vampire Slayer," "Angel," "Firefly," "Dollhouse," and "Cabin In The Woods," all critically acclaimed (if not always successful) genre redefiners marked by witty dialogue, as well as smaller creative projects like "Dr. Horrible's Sing-Along Blog." He had comics credibility, too, being a long time fan, a candidate to direct or direct comic movies dating back to "X-Men" in 2000, and the writer of an excellent run on "Astonishing X-Men" comics.

Whedon went home from his meeting with Feige and wrote five pages of material explaining his plan for the Avengers, also coming up with the tagline: "The Avengers: Some Assembly Required" — riffing on the "Avengers Assemble" slogan from the comic books.

Marvel quickly signed him up to write and direct the movie, stipulating only that he include the Avengers and trickster god Loki, with a battle among superheros in the middle and an epic battle against villains at the end, and that he get the movie out in time for a May 2012 release.

The cast and crew loved it, as actor Clark Gregg told Pascale:

“[The script] was funny and still tongue-in-cheek and really got the tone, the Tony Stark tone of the Marvel universe, and still furthered and explored each one of those characters and those relationships. I found out later from other people involved that had the same reaction—like, oh, wow. Oh, wow. Everybody gets to play. Everybody gets to play, and it’s going to be better than anything we reasonably hoped for.”