Following guest performances from Alanis Morissette and Avril Lavigne, we weren't all that surprised when R. Kelly showed up to duet with Melanie Amaro on his own 1996 smash, 'I Believe I Can Fly,' and their duet soared even though the surprise was spoiled.

The pair shook the seats and the stage with their song, backed by a huge light show that nearly overshadowed their big voices. Thankfully, their stellar showing was not lost on the judges -- or most of them, anyway.

"That is one of the most important songs written in the past 50 years, so you're very lucky to sing that with him," L.A. Reid told Amaro. "You were overshadowed by R. Kelly," he added, which quickly brought on the booing. "It was great, but I expect more from you."

"That song gave you wings," Nicole Scherzinger told her, disagreeing with Mr. Reid. When it came time for Paula Abdul to speak, the audience chanted "Melanie" over her, but her point was clear -- she believes in Amaro.

Perhaps the biggest surprise came when Simon Cowell gave his two cents. "To me, that was an incredible duet," he said, complimenting Amaro without hesitation. "You didn't look like someone in a talent competition, you looked like someone who could be a really important established artist."

Is that what it takes to be the 'X Factor'? We'll have to wait and see!

Watch Melanie Amaro and R. Kelly Sing on 'X Factor'