By Emily Feimster Mary-Kate and Ashley Olsen are keeping plans for their upcoming coming-of-age birthday celebration under wraps. If they decide to go the blowout route, they'll have to fork out some of their big buck to keep up with some of Hollywood's most lavish birthday celebrants. For instance:Oprah Winfrey turned the big 5-0 this year. To celebrate, Stevie Wonder and Tina Turner performed on her show with appearances by John Travolta, Nicole Kidman, Halle Berry, Nelson Mandela, Sydney Poitier, Celine Dion, Maria Shriver, and Jay Leno who pushed out a 400-pound birthday cake. Fifty of Oprah's closest women friends joined her for lunch at the Bel Air Hotel, then there was a dinner party at her ranch in Santa Barbara, and it all ended with a star-studded party including Tom Cruise, Carol Burnett, Julia Roberts, Diane Sawyer, and California's governor, Arnold Schwarzenegger. She reportedly spent hundreds of thousands of dollars but it was a small price to pay for someone who has given over $40 million to charity.

Soon after Oprah's shindig, Travolta also turned 50 and his wife Kelly Preston threw a surprise birthday blowout in Cabo San Lucas, Mexico with 280 of their closest friends. Dan Aykroyd hosted the event with performances by Natalie Cole, Tony Bennett, and an impromptu birthday song from Barbra Streisand. The event held at the One & Only Palmilla resort included celebrity guests Sean Penn, Tom Cruise, Sylvester Stallone, Meg Ryan and Quincy Jones.

Nobody throws a party better than hip hop mogul P Diddy. About 300 guests were flown in on chartered jets to celebrate his 33rd birthday in the Moroccan city of Marrakech, including Naomi Campbell, Ivana Trump, and Tommy Lee. The weekend event kicked off at an exclusive restaurant with Arabian dancers and jugglers and the next night was a party at the home of French-Moroccan actor Jamel Debouze where camels and snake-charmers greeted guests at the entrance. Another party was held at the 19th Century marble Bahia Palace where guests lazed on opulent cushions, ate Moroccan delicacies, and watched dancers perform on flying carpets. The bill was reported to be around $1 million but Debouze was footing most of the expenses. As if Diddy can't afford it!

Party girl Paris Hilton decided to spend her 21st birthday all over the world, throwing parties in Las Vegas, Tokyo, London, Los Angeles and New York - traveling between them all in the same 24 hour period. Each party was estimated to cost $75,000.

When Hollywood hunk Brad Pitt celebrated his 40th birthday, he threw a fancy costume party in which he dressed as his wife's ultimate fantasy, "Duran Duran" heartthrob Simon Le Bon. As a tribute to Brad's film, Jennifer dressed as Helen of Troy and was speechless when he sang one of "Duran Duran's" songs on the karaoke machine.

Following a masquerade party a year earlier, R&B star Usher held his extravagant 25th birthday bash at Pearl in Wes Hollywood. Attendees included former girlfriend Chilli of TLC, Janet Jackson, Jermaine Dupri, Eddie Murphy, Outkast, Brandy, Jimmy Jam, Lil' Jon, and Will Smith. The white cardboard invite contained a CD with all the details for the lavish party in addition to songs accompanying the 1970's theme for the party. VIP guests had a good time with female strippers dancing in fishnet dresses and barely-there thongs.

Well, so much for ice cream and cake.