1 of 10 Ray Michshaw/WireImage.com and Michael Caulfield/WireImage.com
Season 4 champion Carrie Underwood has cleaned up nicely from her Idol days, going from big hair and frumpy gowns to sleek and sexy.
2 of 10 Fox and Stephen Loevkin/WireImage.com
If you block out his dalliance with emo-boy bangs, Season 2 runner-up Clay Aiken has come a long way from his spiky, geeky origins.
3 of 10 Ray Mickshaw/WireImage.com and John Parra/WireImage.com
Perhaps no Idol hopeful has had as complete a transformation as Season 5's Elliott Yamin. New teeth, hair, style and everything have helped propel him forward.
4 of 10 Steve Granitz/WireImage.com and Dan MacMedan/WireImage.com
Color her not purple, but utterly transformed. Season 3 champion Fantasia, aka the single mom with the giant voice, has indeed come a long way, baby.
5 of 10 Ray Mickshaw/WireImage.com and Jemal Countess/WireImage.com
Though she didn't make it as far into Season 3 as she should have, Jennifer Hudson would soon after burst onto the scene with a star-making turn in Dreamgirls, for which she nabbed an Oscar.
6 of 10 Ray Mickshaw/WireImage.com and Mark Sullivan/WireImage.com
Season 5 runner-up Katharine McPhee has made strides not just in her singing life, but her personal life, too. After her debut CD opened at No. 2, she wed boyfriend Nick Cokas.
7 of 10 Ray Mickshaw/WireImage.com and Rick Diamond/WireImage.com
Kellie Pickler has come a long way from mispronouncing "calamari." This Small Town Girl went gold with the hit single "Red High Heels."
8 of 10 Steve Granitz/WireImage.com and Theo Wargo/WireImage.com
Kelly Clarkson, your very first American Idol, has turned into one of its biggest successes. Let's just forget the ill-advised From Justin to Kelly, OK
9 of 10 Fox and Jim Spellman/WireImage.com
Simon once said that Melinda Doolittle should have won Season 6. Having shed the newsboy cap and glammed up, we predict great things for her, too.
10 of 10 Ray Mickshaw/WireImage.com and Steve Granitz/WireImage.com
Though his somewhat spastic dance style and gray hair immediately turned off Simon, Taylor Hicks has stayed true to his Soul Patrol roots and kept the salt-and-pepper (while spiffing up his duds).