Most Memorable Performances

In February, Christina Aguilera got the party started at Clive Davis' annual pre-Grammy bash, held at the Beverly Hilton hotel in L.A. The Grammy-nominated songstress performed recent hits like "Candy Man" for a crowd that included Nick Lachey and Vanessa Minnillo, Sean 'Diddy' Combs, Katharine McPhee, Ashlee Simpson and John Mayer. A few of the lucky guests had also attended the Justin Timberlake pre-Grammy concert the night before.

After flying high above the audience for a spectacular entrance on a giant blimp, Justin Timberlake kicked off the Kids' Choice Awards with a song and dance number. "I say it all the time, I'm too famous to get slimed," claimed a mistaken Justin, who was soon covered in the green goo. Other celebrities who succumbed to Nickelodeon's trademark ooze included Mandy Moore, Tobey Maguire and Vince Vaughn.

At the 2007 MTV Movie Awards in June, Rihanna darted past the press line and into auditorium, eager to rehearse for her big performance of "Umbrella" featuring Jay-Z. The chart-topping tune proved to be one of the most memorable songs of the year, and has already been covered by other artists like Mandy Moore and the Plain White T's.

In a surprise twist, Prince and The Twins provided the soundtrack for Matthew Williamson's Spring 2008 show at London Fashion Week in September. The Purple One played hits like "U Got the Look" and "Kiss" as models strutted the runway in the designer's latest collection. "He really wanted to do this, and you don't say no to Prince," Williamson told Reuters.

50 Cent

, Kanye West, Diddy and Jay-Z were a quadruple threat as they teamed up to perform at New York City's Madison Square Garden for August's Screamfest '07 tour. Though 50 and West were in some serious competition over the release of their much-hyped albums, the duo joined in with the rest of the rap royalty to mix their sweet beats.

In July, Madonna stormed the stage at London's Wembley stadium to do her part for Live Earth. "Let's hope the concerts that are happening around the world are not just about entertainment, but about starting a revolution," she declared. Though the performances by Madge and big bands like The Beastie Boys, Bon Jovi and The Police were a once in a lifetime event, the festivities were just the beginning of a three-year campaign to clean up the planet.

In May, Maroon 5-fronted by heartthrob Adam Levine-jumped on the American Idol bandwagon to perform a song from their latest album It Won't Be Soon Before Long before America said goodbye to the popular Melinda Doolittle. Finalist Blake might have had an advantage: He got to perform the band's hit, "This Love."

"Marc and I are expecting a baby!" a glowing Jennifer Lopez announced on stage during the final stop on their En Concierto tour in Miami, Florida in November. Anthony himself was perhaps the most surprised person in the room, bending down to rub his wife's belly before exclaiming, "I did not expect her to say anything!" Though designer Roberto Cavalli had spilled the beans about the couple's great expectations last week, Lopez's announcement marks the first time she has acknowledged the rumors.

In September, Teri Hatcher made a surprise appearance during a performance by Band From TV-whose regular members include Heroes' Greg Grunberg, House MD star Hugh Laurie and Hatcher's own Desperate Housewives flame, James Denton-at TV Guide's 5th annual Emmy party. Kanye West and John Legend also took turns on the stage to entertain the VIP guests.

"I can't wait to see Britney perform!" was the resounding cry of celebrities like Paris Hilton, 50 Cent and Jennifer Hudson. Britney didn't disappoint, kicking off the show with her new techno-burlesque song, "Give Me More."