The worlds of art, music, fashion, and celebrity met in a perfect storm in Los Angeles this weekend: Gwen Stefani rubbed elbows with Frank Gehry; Jeff Koons mingled with Brian Grazer; Kate Bosworth clinked glasses with Gore Vidal. After gallery openings and book launches, Hollywood’s high-culture weekend culminated in Lady Gaga’s performance with Moscow’s Bolshoi Ballet at the Museum of Contemporary Art’s 30th Anniversary Gala on Saturday night.

Celebs Jessica Alba, Kate Beckinsale, Chloe Sevigny, Eva Mendes, Pierce Brosnan, and James Franco, among others, packed into the Downtown museum to watch the pop princess perform a new song, “Speechless.” Brad Pitt and Angelina Jolie also attended the gala, but spent their time out of the spotlight, quietly touring the museum’s permanent collection. The event, which attracted dealers and collectors from all over the world, was affectionately referred to as “MOCA New,” for its significance in reversing the museum’s recent financial misfortune.

Click the Image Below to View Our Gallery of LA's Art-Filled Weekend

The art-filled weekend began on Thursday night, with the opening of PRISM, a glowing building in West Hollywood, where 23-year-old Australian artist P.C. Valmorbida and Jared Najjar opened “mindthegap,” a vibrant exhibition of geometric art by Barry McGee and Phil Frost. A fashionable crowd that included Rachel Zoe, French Vogue editrix Carine Roitfeld, and Margherita Missoni packed the three-story building—which drove the young, artsy crowd to the hedge-hemmed roof, where, overlooking Sunset Boulevard, they partied late into the night.

The next evening, fashion’s finest cleaned up for the launch of Prada’s new book at its Rem Koolhaas-designed store on Rodeo Drive. Jessica Biel, Chloë Sevigny, Jessica Alba, and Ginnifer Goodwin arrived in a glittering assortment of Prada frocks. The crowd tabbed through pages of Prada’s book—a catalogue raisonné that highlights the fashion house’s involvement in architect, film, and art.

Early on Saturday afternoon, art’s heavy hitters packed Gagosian Gallery in Beverly Hills for a show of Jeff Koons’ new paintings—large-scale, Lichtenstein-inspired works with abstract vaginas painted over each. And the paintings, priced between $2.5 million and $3.5 million, were under close watch: One brawny security guard stood next to every work. It was Los Angeles’ most expensive exhibition to date. But that didn’t scare buyers away—all ten of the paintings reportedly sold.

Studio heads and artists streamed into MOCA on Saturday night—in carefully pressed tuxes and glittering gowns—with the exception, of course, of Los Angeles Mayor Antonio Villaraigosa. “Who are you wearing?” shouted one reporter as he walked down the red carpet. “This?” the mayor responded. “Off the rack!”

The main event didn’t arrive until Saturday night when, just before the chicken was served, Lady Gaga took the stage at the 1,000-person MOCA fete. Pop’s high priestess appeared on stage in a cloud of smoke, wearing a tall velvet crown designed by architect Frank Gehry, which was reportedly too large for her head and had to be sewn onto her just before the show. She donned crystal skirt designed by Miuccia Prada. “Francesco Vezzoli and I were inspired by [Giorgio] de Chirico, and his paintings of the Ballets Russes,” Prada told The Daily Beast of her costumes for Lady Gaga and the Bolshoi. Gaga took her place at a bright pink grand piano designed by the artist Damien Hirst, decorated with his signature blue butterflies, which rotated in smoke as she sang.

As soon as Lady Gaga and Francesco Vezzoli took their final bow, Pop Magazine Editor Dasha Zhukova and her entourage dashed out of dinner to get to her much-anticipated afterparty in a small wooden shed on Sunset Boulevard. And directly after the main event, the crowd followed: Kate Beckinsale, Gwen Stefani, Kate Bosworth, James Franco, Guy Ritchie, Eva Mendes, Rose McGowan, Pharrell Williams, Tom Ford, and artist Takashi Murakami, among others, packed the tiny building (and the PRISM gallery next door) to celebrate the glamorous night.

After the crowd cleared, however, MOCA’s heavy-hitters went back to business: The piano went up for auction and, though it started at $70,000, reportedly sold to dealer Larry Gagosian (who represents Hirst), for $450,000. After the event, rumors abounded about the purchase. One MOCA insider speculated that Gagosian bought the piano as a gift for friend Brett Ratner; another guessed he had purchased it just to protect the price. A prominent artist present insisted that Hirst’s butterflies were merely stickers.

In the end, however, the money went to the museum, which, after a long period of financial turmoil, confidently reemerged into the art world on Saturday night. “Tonight we celebrate the first 30 years,” said founding member Eli Broad. “‘MOCA New’ is, as I like to call it, a new beginning.”

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Isabel Wilkinson is an assistant editor at The Daily Beast.