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OTRC: Elisabeth Moss slams Jeremy Piven as 'unprofessional,' talks Jon Hamm

Elisabeth Moss appears on Bravo's late night talk show, 'Watch What Happens Live,' in May 2013. (Bravo / 'Watch What Happens Live')

Elisabeth Moss didn't "plead the fifth" on "Watch What Happens Live" -- instead, she opted for being brutally honest.

The "Mad Men" actress, 30, appeared on the late night Bravo show that's hosted by Andy Cohen earlier this week. While the casual conversation drifted from topics of "BADvertising" to "Real Housewives," the real dishing began when Moss played "Plead the Fifth."

In each episode, celebrity guests play a game where they can "plead the fifth" if they receive a question from Cohen that they'd rather not answer -- however, Moss opened up about her former co-star Jeremy Piven, who dropped out of their 2008 Broadway show.

After being asked about Piven's sudden exit, Moss responded: "That's a very good one. I could go on and on," she smiled, adding that the actor's behavior was "highly unprofessional."

"We were all surprised," she continued. "It came out of nowhere. He just didn't come back one day."

Piven, known for his roles in shows including "Entourage," dropped out of their stage production, "Speed the Plow," after citing mercury poisoning from "eating too much sushi."

Another hot topic that Moss didn't mind discussing? Jon Hamm's ... well ... junk.

"Is it true what they say about Jon Hamm's ham?" Cohen asked the starlet.

"Well, I mean, we've all seen the pictures so I mean I would suppose so," Moss responded. "That's all I know."

Moss, who started out as a child actress, currently plays Peggy Olson on "Mad Men" alongside Hamm. The show is currently in its sixth season. She has also appeared in "Get Him to the Greek," "The Practice," The West Wing" and "Girl, Interrupted."

Watch Moss' "Watch What Happens Live" interview from the show below! Also, check it out on Bravo's website.

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