Apparently, the week of “Idol Gives Back” will be all about people upending my expectations. First, it was Kristy Lee Cook strutting the stage like a total star, and tonight, during the 150 minute charity concert, it was Fergie, literally subverting my concept of reality.

(Before I begin, let me say that I have it on good authority–from someone who was there–that the charity show was taped on Sunday night. So all those “phone calls” they were taking from the stage? Fake-o!)

Anyway, Fergie. Now see, I don’t hate the woman. If you look on the at my most-played songs on iTunes, you will see that “Clumsy” ranks at number 7 and that “Don’t Lie” by Black Eyed Peas is number 36. When those hot hits come on, just TRY not to work out! I defy you!

And yet… it IS kind of embarrassing that of all the songs I’ve listened to since June 2006, “Clumsy” ranks above almost everything. As insanely catchy as it is, it’s not so much with the musical quality. It’s made of beeps and squeaks and Fergie yelling “Oh!” every two seconds, which is not what Berry Gordy intended when he invented dance music. Until “Idol Gives Back,” Andrew wouldn’t even concede that Fergie could sing, because none of her singles evince any serious musical talent. (And hitting the two notes in “Big Girls Don’t Cry” doesn’t count, as much as I like that song.)

But then? Tonight? Fergie was reborn. First, she wailed her way through “Finally” like she was mistress of the piano bar, and then she performed a duet with Heart and outsang Ann Wilson.

Think about that: Ann Wilson has one of the greatest rock voices of all time, and even tonight, despite decades in the business, she smoked “Barracuda” like it was a cheap cigar.

Fergie, however? Before our very eyes, Fergie turned into a rock goddess. First of all, her vocals on “Barracuda” were ferocious. And she owned that black leather catsuit like her name was Michelle Pfeiffer. And she stalked the stage like it was her personal jungle kingdom. It’s not everyone who can crawl on all fours while singing into the camera and make it seem like perfectly natural–nay, naturally perfect–behavior, but she did it. Her energy was thrilling.

As I was watching her slink around, I literally said, “Fergie’s acquitting herself nicely as a rock star.” And it was like she heard me, because seconds later, she did a one-handed cartwheel. Yes, she did. And then… she did another one. What? Who? Is the ceiling the floor?

My friend Kerri and I watched that moment three times. It was so audacious and unexpected, it was like it hadn’t even happened. Because… really. Can you name one pop superstar currently in his or her prime who would even try something like that? Maybe Pink, but I don’t think her arms are long enough. Otherwise, don’t look for Beyonce to go all circus performer. There’s something totally out of control about busting out a pair of one-handed-carts while standing next to Heart. Out of control, and yet totally in control, because only a performer with all her wits about her could do that and then nail a final note.

To me, that mix of spontaneity and professionalism is pretty damn inspiring. I doff my hat to you, Fergie. If your next album has that kind of pizazz, I will be proud to see its songs in my iTunes top ten.

Note: I’ve since learned that Fergie does this move during many of her concerts, which means it wasn’t as spontaneous as it seemed. And yet… still awesome.