Some of showbiz’s biggest names marked Saturday Night Live’s 40th birthday on Feb. 15 in NYC, and the party was absolutely mahvelous.

Says one eyewitness, “It was a celeb-filled jam session,” with Prince, Martin Short, Bill Murray and more riffing into the wee hours. “Adam Sandler was having a ball — he stayed past 4 a.m.”

Sadly, one of SNL’s most-beloved stars, Tracy Morgan, couldn’t make it as he continues to recover from traffic accident injuries.

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Bill Murray onstage during ‘SNL 40.’

“It was a dignity thing,” costume designer Tom Broecker tells ‘Closer.’ “Until he feels great, Tracy doesn’t want the world talking about him.”

Related Story: Tracy Morgan Wasn’t “Mentally or Emotionally Ready” for TV Comeback on ‘SNL 40’ (Report)

Generations mixed as the current cast met the pioneers: “Jay Pharoah thanked Garrett Morris for being the first black person on SNL,” says an insider. “It was a cool moment.”

Eddie Murphy’s return to 30 Rock after a 31-year absence generated the evening’s biggest buzz.

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Eddie and his girlfriend, Paige, on the ‘SNL 40’ red carpet.

He arrived with his girlfriend of nearly three years, 35-year-old swimsuit model Paige Butcher, on his arm. Legend has it Eddie refused to do ‘SNL’ again after David Spade made a joke about him (“Look, children, a falling star!”) on the show, but the two comics did cross paths at producer Lorne Michaels’ reception the night before the reunion.

To read the full story on ‘SNL 40,’ pick up the new issue of ‘Closer Weekly,’ on newsstands now!