Actress Mary McCormack is best known as shock jock Howard Stern's wife from 1997's Private Parts. Now, she's tackling even tougher, and possibly trashier, subject matter. In HBO's improv series K Street — Sundays at 10:30 pm/ET starting Sept. 14th — she'll dive into the world of Washington politics, under the watchful eyes of executive producers Steven Soderbergh and George Clooney.

Here's the sitch: Real-life political figures like Hilary Clinton guest star as clients of K Street's imaginary PR consulting firm. The "consultants" who work there include political pundits James Carville and Mary Matalin, who play themselves, while actors like McCormack and Ed's John Slattery play characters. Confused yet?

"The idea of the show," explains McCormack, "is that on Monday, we all sort of brainstorm and talk about what is going on in the news that week, like what everyone in D.C. is talking about. We relate it to our fictional PR consulting firm in some way. Then, we go out and actually talk to [political notables], and then it airs that same week on Sunday night.

"It's unusual and it is not scripted," she adds. "It is all improvised. No script, no hair, no makeup."

McCormack seemed to have such a blast with David Spade in Dickie Roberts: Former Child Star (opening Friday). Why switch to such serious stuff? "It is a chance to use all of my brain," the 34-year-old Jersey girl laughs. "And a chance to be in D.C. and learn about government, which I didn't know a lot about.

"I did a movie with Steven Soderbergh called Full Frontal — which not a lot of people saw," she chuckles. "But we did do a lot of improvisation and I like working like that. This is harder, because it is [me] improvising about the reconstruction of Iraq and as a Republican and in a jargon that I am not familiar with. It is like improvising ER. It is in another language, almost."