Gene Kelly, Ginger Rogers, Ann Miller . . . That’s Entertainment!

If Old Hollywood ever has an official last hurrah, it probably won’t be markedly different from Thursday’s benefit black-tie premiere of MGM’s “That’s Entertainment! III” at Mann’s National in Westwood.

The searchlights were burning and the red carpet was rolled out for the stars who made the spectacular MGM musicals of the ‘30s, ‘40s and ‘50s. Limo after limo arrived with guests, including Gene Kelly, Ann Miller, Cyd Charisse, Esther Williams, Ginger Rogers, Rita Moreno, Margaret O’Brien, Gloria De Haven, Fayard Nicholas and Janis Paige.

“This cast will never be assembled again,” said director George Sidney, whose credits include “Anchors Aweigh” and “Show Boat.” “Let’s face it. If they ever get around to doing a fourth one of these, a lot of us won’t be here for it.”

The arrival process was such a show in itself that guests pressed against the National’s second-floor windows to watch Army Archerd, in time-honored tradition, interview the stars. The glamour of the scene made it as much a fashion show as a premiere.

Although more than half the guests were older than 60 and some of the gowns might have last seen service at an Eisenhower inaugural (it’s been a while since a fox fur jacket was seen at a movie premiere), it was still an amazing sight. At one point it looked as if half the world’s supply of gold lame was passing by.

“I just love this,” one woman said. “Look at Ann Miller. Her hair is like a fabulous black croissant.”

It wasn’t just the fashion that got rave reviews. Film critic Leonard Maltin said: “I’m defenseless. I have no resistance to this movie. There’s no way to criticize it. It’s just such a thrill to see this on the big screen again.”

Post-screening, the 1,100 guests made their way down 200 yards of red carpet to the Armand Hammer Museum for the after-party. Or at least some of the guests walked. A dozen limos were waiting to take the film’s stars the short distance to the party, which netted more than $150,000 for the American Film Institute.

Inside the Hammer, there were buffets from Ambrosia of caviar, oysters on the half shell and Cajun sand dabs, although most of the crowds were around the MGM stars.

Paige was saying how “proud she was to be of that era.” Williams was being told, “your stuff is timeless,” by one less than verbally adept admirer. Rogers talked about how the evening “brought up so many memories.” And Charisse said these kinds of lavish musicals will never come again: “It’s the end of an era.”

Although there were younger stars at the event, on this night they had secondary status. Ted Danson and Mary Steenburgen talked with MGM CEO Frank Mancuso. Jeff Bridges was on hand with his father, Lloyd, and sisters Jennifer and Meg Tilly strolled through the museum’s courtyard together.

The Tilly sisters said the film had a strong effect on them. “It made us glad we’re stars now,” Jennifer said. “Back in the ‘40s you had to sing, you had to dance, you had to be phenomenally talented.”