The scene: A fiesta-themed birthday party for...

The scene: A fiesta-themed birthday party for Armand Hammer, the 91-year-old physician/ glasnost enthusiast/museum builder/cancer research supporter, at the Beverly Hilton on Sunday night. While most people are satisfied celebrating a birthday with a few friends, barbecue, brewskis and a couple of Springsteen CDs, Hammer opted for a few hundred friends, a four-course meal, champagne and live entertainment that included Isaac Stern and members of the Los Angeles Philharmonic. The man knows how to par-tay.

The buzz: While most of Dr. Hammer’s friends (those thisclose to him call him “Doctor,” as in, “You can speak to Doctor now.”) are well aware of how spry he is. But there are always those who are stunned by the fact that he doesn’t seem 91. The other talk running around the ballroom was of the appearance of the McGuire Sisters and the recent Dominick Dunne profile of Phyllis McGuire in Vanity Fair that concentrated on her relationship with Mafioso Sam Giancana.

Who was there: Frances and Armand Hammer, Helen Hayes and son James MacArthur, Mr. and Mrs. Morton (Dear Abby) Phillips, Dr. Mathilde Krim, Gloria and James Stewart, Jane and Jerry Weintraub, Dr. Robert Gale, Lori and Mike Milken, Jean and William French Smith, Sen. Albert Gore Sr., Cesar Romero and Sybil Brand, Lilly and Brandon Tartikoff, Art Linkletter, Sherry Lansing, Jack Haley Jr., Nancy and Zubin Mehta, Norman Cousins, Barbara and Marvin Davis, Barbara Walters and Merv Adelson and Carmen Zapata.

Dress mode: The fiesta theme seemed to bring out the flounciest dresses. Jane Weintraub opted for an off-the-shoulder metallic purple gown; Lilly Tartikoff bared her shoulders in a shirred strapless black dress; Sherry Lansing also went for black strapless; Barbara Walters appeared in an all-over-pleated gown in pastels.

The food: Louisiana blue crab cakes with tartar sauce and a sweet-sour salsa, fiesta salad, filet mignon with asparagus, broiled tomatoes and spinach fettucine, and a sugary birthday cake with strawberries.

Entertainment: Serenading the audience was Mariachi “America” with Viviana Montez, members of the Los Angeles Philharmonic conducted by David Alan Miller, cellist Mstislav Rostropovich (“Slava hasn’t missed a birthday yet,” Hammer said), violinist Isaac Stern and baritone Sherill Milnes. Later the McGuire Sisters (in matching sequined peach gowns) sang with the Coconut Ballroom Orchestra conducted by Mort Lindsey. Dr. Hammer conducted the Philharmonic in “Stars and Stripes Forever” as the guests clapped along, and had “Happy Birthday to You” sung to him by Jane Weintraub and the audience. Danny Thomas emceed it all.

Theme dream: he Mexican fiesta theme was carried throughout the ballroom, beginning with pillars draped with colorful streamers and an archway proclaiming, “Feliz Cumpleanos. “ Guests could have their pictures taken by an ersatz Mexican street scene, complete with sombreros, pottery jugs and flowers. Centerpieces were wheelbarrow miniatures stuffed with flowers, and the wheels had been painted to read, “Viva Armand.”

Quoted: Hammer revealed that 56 years ago, he had a crush on Helen Hayes, but after dining together one night, “Nothing came of it,” he said. “You were married and so was I.” He also used his platform to make yet another plea to help fund cancer research. “I believe we can put every scientist to work who needs funding,” he said, “so we can give our children and grandchildren a cancer-free world.” This party wasn’t a fund-raiser, but it wouldn’t be surprising if Dr. Hammer caused a few wallets to open anyway.