A famous ensemble cast, a critically-acclaimed play and a director that brought him to fame with “ER” were several reasons for George Clooney to become a producer on dark comedy “August: Osage County.” But why did he really do it?

“It was the cash, honestly,” he joked at the Nov. 8 American Film Institute Festival screening of the film.

He, director John Wells and stars Juliette Lewis, Julianne Nicholson, Dermot Mulroney, Misty Upham and others involved with the movie gathered at the TCL Chinese Theater in LA to celebrate the AFI premiere of the adaptation of Tracy Letts’ play of the same name. Meryl Streep, Julia Roberts, Chris Cooper and Margo Martindale also star in the movie Letts also wrote about a highly dysfunctional family.

Wells explained that he first saw the show on Broadway not knowing he was going to be involved, and despite the dark content, he remembered that he “laughed like crazy.”

“I felt kind of bad about laughing, because some of the stuff you’re laughing about, you’re like ‘Ohhh, I shouldn’t be laughing about that!'” He recalled. “I think it explores a lot of the ways that families really work.”

Clooney took on the film with his producing partner Grant Heslov, and the two explained that because most of the movies they’ve done together are male-oriented, such as “Good Night and Good Luck” and “The Ides of March,” doing a female-centric film would be a good idea. Harvey Weinstein’s The Weinstein Company acquired the rights to the adaptation, but it was something the duo had their eyes on.

“The truth is, we actually chased this,” said Heslov. “We tried to get the rights to this, and Harvey-“

“Beat us,” Clooney finished.

When it was time to shoot, they said there’s no bossing Streep around, but they learned how to work with Roberts pretty easily.

“As you well know, Julia is an alcoholic,” Clooney jested. “It was easier to work with her because you just offer her booze, apply that with anything.”

“She’s no good after 11:30,” Heslov added.

For Nicholson, known for roles in series including “Masters of Sex” and “Boardwalk Empire,” working with the famous, older women was a crash course in acting.

“No one does tips,” she said. “You learn by osmosis. You’re in a room with Meryl, you just sort of sit and watch and hopefully something will rub off or sink in there.”

Young thesp Upham appears in the film as a housekeeper for the unconventional Weston family, and was a housecleaner before landing the job of a lifetime.

She said she was so nervous before shooting that she couldn’t eat, and she obsessed over the script. When she got on set, however, it turned surreal when surrounded with her cast.

“I turned around and Julia Roberts was standing right there, and she was just like, ‘Hi, Misty!’” She remembered. “I never once in my life thought I would ever hear Julia Roberts call my name.”

Though the film isn’t even out yet, Roberts’ and Streep’s performances are already being praised, and murmurs of Academy Award noms are attached to the comedy. Even so, Mulroney said he’s going into it without expectations, and he’s just enjoying what’s happening now. Plus, he has a certain hope of what viewers will take out of it.

“I hope that they’ll laugh while they recognize how crazy these people are, and maybe see some of their own family in how people’s dynamics degrade over time and how they try to preserve them,” he said. “Sometimes you can’t. It’s really a sad movie in some ways and hard, but hilarious.”

“August:Osage County” will be released Christmas Day. AFI Fest runs through Nov. 14.