Billionaire supermarket mogul John Catsimatidis marked his birthday with a weekend Hamptons bash featuring comic Joe Piscopo crooning, “That’s Life” and speeches by Rudy Giuliani and Curtis Sliwa.
At the Southampton soirée for the WABC owner, who turns 73 on Tuesday, former “Saturday Night Live” cast member-turned-local radio host Piscopo belted out a rendition of the Frank Sinatra classic, according to video obtained by The Post.
“That was one of the greatest parts of the evening. Everyone was singing,” an attendee said.
Former New York City Mayor Giuliani also spoke to party-goers about the significance of the upcoming 20th anniversary of the Sept 11 attacks on the Twin Towers.
“Rudy spoke of the heroism of the 9/11 responders, particularly the firefighters,” the source said.
He and Piscopo also led the 300-person crowd in singing Sinatra’s “New York, New York.”
Meanwhile, Sliwa — the host of a WABC show who is now the Republican candidate for mayor — asked revelers to vote for him when he faces Democratic Brooklyn Borough President Eric Adams in November, the source said.
The pitch came after a top campaign staffer for Sliwa, the founder of the Guardian Angels, recently ripped Adams for getting “wined and dined” in the Hamptons. Catsimatidis hosted a fundraiser for Adams in the Hamptons this past summer.
The conservative mogul, who is friendly with both candidates, also recently dined out at Italian restaurant Rao’s in Manhattan with Adams.
Rep. Lee Zeldin of Long Island, a Republican gubernatorial candidate, ex-Gov. David Paterson and former US Rep. Pete King attended Catsimatidis’s party, which was held at the Dormition of the Virgin Mary Greek Orthodox Church of the Hamptons.
Also whooping it up at the blowout was Suffolk County Executive Steve Bellone; private eye and former NYPD Detective Bo Dietl; former Westchester County Executive Andrew Spano; public-relations maven Todd Shapiro and former state Comptroller Carl McCall and his wife, Joyce Brown, president of the Fashion Institute of Technology, according to the tipster.
Hefty portions of Greek food — including moussaka and pastitsio — were served at the birthday bash to honor the Nisyros-born Catsimatidis’s heritage. Some 10,000 plates were also broken to get rid of “frustrations,” a source said.
“Everything was celebratory in honor of Cats,” the source noted.
Additional reporting by Ian Mohr