Andy Cohen knows exactly how to get under “Real Housewives of Orange County” star Vicki Gunvalson's skin: Bring up her ex-boyfriend Brooks Ayers.

That's exactly what he and a "Watch What Happens Live" caller did on Monday night, and Gunvalson wasn't having it. When the caller asked what the current status was with her old beau and the cancer deception that was a major focus point of the Bravo series, Gunvalson lost her cool.

“Why doesn’t anybody talk about Donn? I was married to Donn for 20 years. I dated Brooks for 4 and a half. It’s like, come on,” the flustered reality star said. “We weren’t engaged, we weren’t married, it was a boyfriend for a limited bit of my time. There is no status with Brooks. He has moved on, he is in Indiana.”

Cohen delighted in telling "WWHL" viewers that "she went nuts" when he pulled a prank on Gunvalson before the show, telling her "we had a huge Brooks thing we were planning."

But perhaps Cohen got the Brooks segment he wanted after all, because the caller's question prompted him to ask another: "What does Brianna think about you still missing and confessing to loving Brooks?"

She denied harboring any remaining feelings for him, but did make it clear on "WWHL" that she does have some questions for her ex.

“Why did you lie to me? When are you going to pay me back my money? That's what I want to know,” she said.

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