Celebrities really do all know one another, Randy Jackson explained, as he schmoozed and hugged Jill Zarin Saturday night. They meet at events, like the Phoenix House party he was co-hosting with Nick Cannon, that also attracted Katie Lee Joel, Kelly Killoren Bensimon (seen here with Jackson), the Countess LuAnn de Lesseps, “Jersey Shore” stars Jenni “JWOWW” Farley and Vinny Guadagnino, as well as stars from “Hell’s Kitchen” and MTV’s “Downtown Girls.”

“We meet at various events like this one,” he told us. “Bethenny’s a friend of mine, so Jill and I go back.” That’s way back. “Jethenny” is way over.

advertisement | advertise on newsday

Jackson has spent plenty of time in the Hamptons, hanging out with friends, including honoree Charlie and Lauran Walk. But this time, he was heading right back to LA.

He’ll be the last original judge next season on “American Idol.” With the Simon Legree judge leaving, will Randy get a little meaner? “Nooooo,” he said. “The dog is the dog! The dog never needs to change.” Next season, he promised, “a lot of heat, a lot of big change. We’re looking at everything. We’re taking some ideas and seeing where we go with it.”

Just promise to come back to the Hamptons. “Of course,” he assured us. “Maybe I’ll move out and do the show from here. It’d be wild!”