The biggest costume party in the desert Saturday was Phish Festival 8.

The band's publicist Erin Cooney said at least 40,000 people attended the event at the Empire Polo Club in Indio and a large percentage of them showed up in costumes as elaborate as a team mascot or as simple as a box over shoulders.

The Vermont-based quartet celebrated the holiday with “a musical costume,” teasing Phish fans with the opening strains of Michael Jackson's “Thriller” before segueing into a video remix of the 99 albums it had hinted at performing on its Web site. They then launched into the Rolling Stones' classic 1972 double album, “Exile On Main St.,” supplemented by a horn section.

Many of the young Phish fans hadn't heard of “Exile” before the 7:30 p.m. set.

“No,” said Becky K. of Indianapolis, Ind., who came with her sister wearing matching serapes and sombreros. “I was hoping for Michael Jackson. But I just like to hear them play and dance all night.”

But another fan who had been hoping Phish would play “Exile” said it was everything he expected, especially with Sharon Jones of The Dap-Kings singing back-up vocals.

“I've seen the Stones a bunch of times,” said Jon Whetstone of Lansdale, Penn., noting that the Stones have two guitarists and Phish singer-guitarist Trey Anastasio played both parts.

Each member of Phish took a turn on lead vocals, with Anastasio kicking off the set on “Rocks Off,” pianist Page McConnell taking lead vocals on “Rip This Joint,” bassist Mike Gordon singing lead on “Shake Your Hips” and drummer Jon Fishman providing lead vocals on “Sweet Virginia,” including the line, “Yes, I've got the desert in my toenails.”

“Sweet Virginia” evoked a cheer from the heavily East Coast-based fans when Fishman sang, “Thank you for your wine California.” But the biggest cheer of the night for a song was for “Loving Cup,” a song Phish has covered before and is available for downloading.

“I think it was awesome,” said Drew Bolding of Kokomo, Ind., of the choice to play “Exile.” “That was my first choice. With the 99 albums (Phish was teasing its fans about playing), I was expecting something creepy, like a 100th album to pop up.”

Phish didn't stretch out into any long jams with 18 songs on “Exile” and a final set due to start at 10 p.m., but Anastasio provided some extended guitar solos on “Casino Boogie,” and the band created a longer and darker version of “Ventilator Blues.”

Phish fans generated an exceptionally friendly vibe at the festival in large part because of extreme satisfaction with the festival.

“It's been the most modern, wonderful festival,” said Debbie N. of Olympia, Wash. “Everything is done with the comfort and joy of the people here in mind.”

Indio Police Department spokesman Ben Guitron said that as of 9:45 p.m. there had been 16 arrests, mostly drug related, and no problems with traffic. He referred crowd size questions to the promoter, Paul Tollett of Goldenvoice, who didn't return attempts to reach him for comment.

Tollett said earlier he expected as many people as the Goldenvoice-produced Coachella Valley Music and Arts Festival, which attracts 50,000 to 60,000 people a day in the spring.