Debra Messing Debra Messing

Jeremy Piven's guest-starring turn on Will & Grace as the ex-boyfriend of Debra Messing's character was unforgettable for Messing - but not for the reasons you might think.

"The very first day of rehearsal, he shoved his tongue all the way down to my heart," Messing told Andy Cohen on Watch What Happens: Live this week. "I was just like, 'Whoa!' ... Every time, he went for it."

Piven appeared on the show in 2000 as Grace's former boyfriend, who asks her to join him and his current girlfriend for a threesome. Messing says that, thanks to their sloppy lip-locks, she "wasn't a fan" of the Entourage alum at the time.

Fall Preview: Which shows will you add to your Watchlist?

Her favorite male co-stars were Harry Connick, Jr., who played Grace's husband Leo, and Bobby Cannavale, who played a love interest of Will's (Eric McCormack), she told Cohen.

Watch Messing's Watch What Happens: Live appearance here: