Justin Bieber: Most Tweeted Celebrity for 2012!

Justin Bieber shows off his abs while performing during Hot 99.5′s 2012 Jingle Ball held at The Patriot Center on Tuesday (December 11) in Washington, D.C.

The 18-year-old entertainer was joined by a guitar-rocking Ke$ha and Enrique Iglesias.

PHOTOS: Check out the latest pics of Ke$ha

Over the weekend, Ke$ha and Justin were both spotted at 92.3 FLZ’s 2012 Jingle Ball Concert in Florida.

It was recently announced that Justin is the most tweeted celebrity of 2012, according to USA Today.

35+ pictures inside of Ke$ha, Justin Bieber, and Enrique Iglesias performing in Washington, D.C…