Today marks the big 3-0 for fashion's favorite set of twins, Mary-Kate and Ashley Olsen. While they've got quite a reputation for hosting their own fabulous bashes (ahem, cigarette-filled weddings and the like), these birthday girls are also notable - and notorious - attendees. Through the years, they've partied their way from New York to Paris and back, mixing drinks, dressing brides, getting slimed. Click through for their best party guest moments. 

[Photo courtesy Getty]