"She put out a tweet and says: 'We need to come together, let's talk. Really, let's talk'," Watters said, reading the tweet -- which also listed a phone number with a Manhattan area code.
"So I'm going to call the phone number and I'm just going to try to talk to her and see what she says. Let's call her right now.
"You can't say you want to bring people together and then you want to blacklist people because that just hurts their families, that hurts the entire industry," he continued, as ringing was heard on his cel phone.
After a few rings, Messing's voice appeared.
"Hi there, it's Debra. Yep, that's right, it's me," the message began.
"I'm not going to be listening to this because I'm only going to be reading your texts, so please text me."
Watters then hung up, remarking, "That's not 'talking,' that's a scam, Debra."
"I feel like she's already been blacklisted, I haven't seen her in years."
From 1998 to 2006, the original iteration of "Will & Grace" aired on NBC, with the network later rebooting the series in 2017.
On Twitter, co-star McCormack echoed Messing's message, asking The Hollywood Reporter to, "kindly report on everyone attending this event, so the rest of us can be clear about who we don’t wanna work with."
The call for a list of attendees gave rise to a backlash from both sides of the aisle, with left-leaning "View" moderator Whoopi Goldberg denouncing the idea as potentially dangerous and evocative of the Hollywood blacklist era of the 1950s.
"The last time people did this, people ended up killing themselves. This is not a good idea, OK?” Goldberg said, referencing former Sen. Joseph McCarthy, R-Wis., who led a Cold War effort to oust accused Communists from Washington, Hollywood and other spheres of influence.