Simon Cowell's group Alex and Sierra performed 2 songs last night on "The X Factor." On Dec. 5, 2013, the duo reached #1 on iTunes with "Say Something." Alex and Sierra also took the #13 spot with the other song they sang last night, "Say My Name." This is the highest anyone on "The X Factor" USA has ever ranked for a performance song. Other "X Factor" acts who ranked high on iTunes this week are Restless Road and Jeff Gutt. A Great Big World and Christina Aguilera's version of "Say Something" is currently at #3 on iTunes. A Great Big World tweeted to Alex and Sierra, "WOW! Huge congrats to @alexandsierra3 for your version of "Say Something" from @TheXFactorUSA reaching #1 on iTunes!!" Even though Alex and Sierra's "Say Something" performance was the highlight of last night's show, Sierra was actually very sick. Sierra says, "I can say it now since we've already performed and it's not an excuse. I'm really sick. I got one of those shots in my bum." Alex adds, "That's why she's talking at 7 million miles per hour!" Nobody had any idea that she was so sick which just shows how professional Sierra is already.