Every year, stars hit the red carpet of the Grammy Awards in a fabulous outfit and then sometime in between the show and the afterparty, they change into another. This year the sexiest transformation award goes to Katy Perry, who looked smoldering in a Zac Posen Spring 2010 nude number at the Awards Show, later changing into a sexy, boob baring metallic number for the EMI post Grammy Party at the W Hotel in Los Angeles.

PHOTOS: Stars Get Glam For Post Grammy Bashes

Rihanna, also showed off a Good Girl Gone Bad Style Transformation, changing out of her Edwardian-like, high necked gown, into a sultry nude and metallic number.

PHOTOS: Rihanna Sexes It Up For Post-Grammy Party

Who else heated up the afterparties? Check out the gallery in Style to find out.