"Mad Men" star Elisabeth Moss recently caused a stir by calling out Jeremy Piven's lack of professionalism on Andy Cohen's "Watch What Happens Live" on May 23.

During the "Plead the Fifth" segment, host Cohen bluntly asked if there were other reasons for Piven's sudden exit from the Broadway show "Speed-the-Plow" on December 17, 2008.

"That's a good one, that's a very good one," said the 30-year-old actress with a smirk.

"I could go on and on."

But she settled with the to-the-point comment, "Being highly unprofessional."

"It came out of nowhere. He just didn't come back one day."

The show, which marked Moss' Broadway debut, ran from October 3, 2008 until February 22, 2009, reported Radar Online.

"I saw him like a month later at the Golden Gloves, when he was supposed to be really sick," she added.

Piven, 47, is perhaps best known for HBO series "Entourage."

His sudden departure caused "Speed-the-Plow" playwright David Mamet to teasingly say that the actor was leaving to pursue "a career as a thermometer," according to Playbill.com.

But this wasn't the only hot question that Moss calmly navigated through.

Andy Cohen also asked, "Is it true what they say about Jon Hamm's ham?"

In response to Hamm's famous habit of not wearing underwear, Moss giggled and replied like a professional.

"Well, I mean, we have all seen the pictures, so I suppose so. That is all I know."

The "Mad" actress is one cool customer.

Watch the hilarious segment below: