UPDATE 3: Here are a few details on Britney's performance:
Britney sung a portion of "Human Nature" with Madonna, wearing a white top and sexy tuxedo pants. Our source said Britney looked "amazing & energetic." After Britney's appearance, they lowered her off center stage; fans were going nuts.
Word on the street is Britney might make a second appearance. But don't hold your breath. :GASPS: