Kors, acting as a guest panelist, Posen, Heidi Klum and Nina Garcia were one big happy family when they took their seats at Lincoln Center to watch the collections of this season's contestants. (Kors and Klum joked they've spent so much time together over the years that they now look like brother and sister.)
"I didn't call Zac with any tips before he started. He knows what he's doing," Kors said in a preshow interview. "I knew I was leaving it in very capable hands."
Chiming in, Posen added: "I had 10 seasons to watch Michael, and I had been a guest judge with him. I'm sure I learned a few things."
The show is the godmother of fashion reality TV, now in its 11th season. It was time for a change, said Klum, who is an executive producer. Kors' schedule forced the switch, but it's been good for the show.
"Of course, I miss Michael, but I talk to him A LOT, and the show has his blessing," she said.
The other new wrinkle this go-around is that the contestants have been working in teams - and they are not necessarily happy about it, Klum said.
"Project Runway" has outlasted some other competition shows because it opens a window on something people are always curious about," she said. "I never saw this as only a reality show. I see it more as a documentary that shows you how clothes are made, how designers get them to fit, how they find the fabrics."
Also, noted Garcia, fashion should never be the same for more than a season.
Sometimes the show's designers tap into the broader zeitgeist that is unfolding on the other catwalks at Mercedes-Benz Fashion Week, she said, and that bodes well since it means they see fashion in the broader context of pop culture.
What the judges saw Friday ranged from cool, edgy leather numbers and intricate red-carpet gowns to somewhat unfinished looking frocks. The audience didn't know which collection belonged to which contestant because the show is only three weeks on air, and producers felt it would give away too much to reveal who made it to this stage.
Posen said he found himself more emotionally attached to some than others, but he was trying not to let that influence his votes.
"Think of the opportunity they're all being given. They can take it from here. They are in the big tent, and they have that for the rest of their lives," he said.
Follow Samantha Critchell on Twitter at http://twitter.com/AP-Fashion