Leona Lewis
Simon Cowell's protégée trotted out her smash hit "Bleeding Love." And it apparently made her "Happy," because she was back the next season, too.
Jennifer Hudson
The Oscar winner didn't need to sweat through 12-hour rehearsals as a contestant to reveal a bangin' new bod.
Annie Lennox
The Eurythmics frontwoman couldn't help but break hearts with "Little Bird" and "Universal Child."
Seal
We're still waiting for him to do Project Runway, though...
Jessica Simpson
The fashionista went country with "Come on Over."
The Jonas Brothers
Nick, Joe and Kevin burned up the DWTS stage on more than one occasion.
Sheryl Crow
"All I Wanna Do" and "Out of Our Heads"
James Blunt
Who doesn't want this guy serenading the room with "Carry You Home" at some point? Coincidence: ex Petra Nemcova ended up being a contestant a few seasons later.
Avril Lavigne
The "Complicated" singer performed her signature tune.