Andy Cohen Reflects on Asking Oprah Winfrey If She'd Ever 'Taken a Dip in the Lady Pond' (Exclusive)

Andy Cohen is looking back on 15 years of chaos in the clubhouse.

As Watch What Happens Live celebrates its 15th anniversary, Cohen is reflecting on some of of his biggest gets and regrets in an exclusive rETrospective interview with ET. Among the most unforgettable was Oprah Winfrey's 2013 appearance.

"This was a huge moment for me and for the show," Cohen says, looking back on footage of the moment. "I'm such a fan of Oprah."

By the end of the interview, Cohen's devil-may-care attitude took over as he seized an opportunity to ask her whether she's "taken a dip in the lady pond."

"That's probably one of my few regrets," Cohen says.

"It meant so much to me that Oprah Winfrey did the show," he continues. "It's gone brilliantly and I turn around and ask her if she's every had sex with a woman. I mean, couldn't I leave it alone?"

At the time, Winfrey answered with a direct, "No, no I have not. Thank you."

Cohen says that the media mogul was "super cool" and "it was not awkward" after the cameras stopped rolling. However, he later heard from Winfrey's pal, Gayle King, that the former talk show host may not have understood the question.

"Gayle King told me later that week that Oprah didn't know what I meant by 'the lady pond,'" Cohen shares. "I thought I explained it pretty well there, but listen, I was so grateful that Oprah did the show and I still am. That remains, I think, my favorite episode."

As for one of his favorite guests, Cohen has high praise for Patti LuPone.

"I mean, Patti LuPone has no F's to give so she is the perfect clubhouse guest," Cohen gushes. "She's been here many times."

LuPone memorably took aim at Madonna during a sit-down in 2017 with Cohen, when she called the Evita star "a movie killer."

"This clip got me in a lot of trouble with Madonna, who called me a 'troublemaking queen' from the stage of her Celebration Tour. [She] said, 'You need to stop talking crap about me on your show,'" Cohen laments. "Now the truth is, it wasn't me talking crap about her. It was people like Patti LuPone -- who I also love, by the way."

Cohen says he ended up sending Madge a highlight reel of "all the nice things we said" about her through the years.

"She appreciated it," Cohen adds, noting that she still has yet to accept his invitation to be a guest on the show after more than 15 years of requests.

"The secret to the success of Watch What Happens Live, I think, is spontaneity, authenticity, fun, humor, me going there and people never knowing what's gonna happen," Cohen muses of his guests' experiences. More often than not, that includes booze.

"People let their guard down here," he says. "It's also live, we're on at night, we serve alcohol."

He adds, "It's so small in here that it's deceptive, like, people don't realize they're actually on television."

One such occasion came in 2011 when Regina King and Jackée Harry were, in Cohen's words, "sauced."

"They were smashed in the green room and they were more smashed the longer we went on," Cohen recalls. "I was wondering if it was too messy and then I realized, 'Oh, wait, people on Twitter are loving this' and it became a really, really historic episode."

Cohen himself has been known to imbibe alongside pal Anderson Cooper during the duo's New Year's Eve telecast on CNN.

"The friendship I have with Anderson means a lot," Cohen says. "We've gotten so much closer over the past 15 years. We've been on tour together, we co-host New Year's Eve together, we've been through a lot and being dads together has been a great joy in our lives."

Today, Cohen is a dad to son Benjamin, 5, and daughter Lucy, 2. Anderson is the father of two sons -- Wyatt, 4, and Sebastian, 2.

"Being a dad has totally changed how I approach work, too," Cohen adds. "I come, I do my thing, I go home to the kids and I love bringing them here."

It's a stark contrast to the way it all started back on July 16, 2009, when WWHL first debuted.

"I used to go out every night until all hours after the show, and now I really stay home," he confesses. "I go home and kiss my kids goodnight while they're sleeping and I can't wait to see them in the morning. My life has totally changed and I wouldn't have imagined this for myself 15 years ago."

The host and Real Housewives mastermind says he's "incredibly grateful" these days.

"The next chapter of life is really all about the kids," he shares. "And keeping this show going and keeping the Housewives as fresh as we can."