When Jennifer Lopez announced she is headed to Las Vegas next year [1], we knew only to expect the most dance-filled, energetic show ever — but after she gave us a little preview of what's to come on The Ellen DeGeneres Show, we can barely contain ourselves. J Lo performed a Vegas-inspired medley of her greatest hits, including "Jenny From the Block," "On the Floor," and "Get Right." Watch the amazing performance, above, then watch her sing "Back It Up" [2] at the American Idol season finale.