Then & Now: American Idol Stars Transform

The 27-year-old from Oklahoma and winner of season four has transformed from a small-town girl to a sophisticated superstar. "If you try and sum up what star quality is," says judge Simon Cowell, "it is a sense of style-a sense of knowing who you are, a sense of being an individual and obviously having a good voice." Underwood's got it all. For the past three years, Underwood has been named one of People magazine's Most Beautiful People. The newlywed beauty has five Grammys under her belt.

Try on Carrie Underwood's many hairstyles now!

The 29-year-old season eight runner up might have been edgiest artist to appear on the show. Since Idol, he's refined his pop-punk look with more eyeliner, skinnier ties, and gravity-defying hair. Lambert won Best New Artist at the Teen Choice Awards in 2009, and his single "Whataya Want From Me" was nominated for a Grammy in 2011.

Try on Adam Lambert's hairstyle now!

Gone is the girl from Texas in pigtails and crop-tops. Since becoming America's first Idol almost nine years ago, Clarkson has transformed into a bonified star who opts for subtle styles on the red carpet. Here, the two-time Grammy winner (whose album sales surpass 18 million worldwide) shows her star power in a feminine little black dress.

Though she finished in seventh place during the third season of the show, she's made it to the top now, winning an Oscar, Golden Globe, and SAG award for her supporting role in Dreamgirls. Her self-titled first album won a Grammy, and she's since starred in Sex and the City and The Secret Life of Bees. After becoming the spokesperson for Weight Watchers in 2010, Hudson underwent a complete body makeover, shedding 80 pounds.

Season five runner-up McPhee has enjoyed many successes since her stint on Idol, including gains in the fashion arena. McPhee performed at the Jane Seymour Open Hearts Foundation Inaugural Celebration, pairing her vivid one shoulder dress with a bold lip and sleek updo.

The Arizona beauty-and winner of season six-is ready for her close-up, thanks to more stylish fashion choices and long, sleek tresses. Recently, Sparks launched her own perfume, and is working on her third studio album.

Gone are the days of the jumpsuit for season three's winner. Barrino, who took her role from Broadway's The Color Purple on the road, has become an elegant figure on the red carpet. She was also the star of her own VH1 reality show Fantasia For Real, and her single "Bittersweet" won a Grammy in 2011 for Best Female R&B Vocal Performance.

"We have a lot of people on the show, towards the latter part, to help contestants with their style and image," says Cowell. Aiken was one who was subject to such help, getting a makeover of spiky hair that became his signature look on the show. Nowadays, the 32-year-old from North Carolina has swept back his hair, filled out his lanky figure, and welcomed a baby boy.

To many, he was the guy with the big hair during the first season of Idol. But as the season progressed, he became known as equally for his vocal talent, ending as runner-up to none other than Kelly Clarkson. Since then, Guarini's started his own production company, Justice Entertainment, Ltd., made his Broadway debut, and toned down his look by sticking to buttoned-up ensembles and closely-cropped locks.

Sanjaya Malakar of season six was one of the most-talked-about contestants on Idol, and was better known for his wild hairstyles than his singing. Recently, Malakar trimmed his tendrils, but kept the rest of his look constant, Converse sneakers and all.

American Idol

's main man Ryan Seacrest has had many different looks since the show kicked off. During season one, Seacrest rocked boyband-esque blonde hair. These days, he has returned to his roots as a brunette.

Dubbed the "Velvet Teddy Bear" by Idol fans, season two winner Ruben Studdard was seen in a casual outfit with a matching fitted cap at his audition. Studdard has since traded in his jeans for a crisp gunmetal suit, but still found a hat to match his getup!

Kimberly Locke wore an all-white getup with a coordinating poncho at the American Idol season two finale. She was known for her soulful voice and sugar-sweet personality. After appearing on VH1's Celebrity Fit Club and a brief run as spokesperson for Lane Bryant, Locke recently debuted her svelte figure in a flattering sequin dress.

DeGarmo was only 16 when she took the title of season three's runner-up. Since that time, she's become a Broadway actress (starring in Hairspray, The Toxic Avenger Musical, and Hair) and changed her look from girly to elegant, while maintaining an element of fun. Case in point: This crimson mini with the extra-long train.