In this photo released by CBS, host David Letterman, right, and comic Jay Thomas get ready to throw footballs at the Late Show Christmas tree during the annual Late Show Holiday Quarterback Challenge on the set of "Late Show with David Letterman," airing Thursday, Dec. 23, 2011 on the CBS Television Network. Thomas and Letterman each take turns tossing footballs at the Late Show Christmas tree to try and knock off the giant meatball perched at its top. (AP Photo/CBS, John Paul Filo)

In this photo released by CBS, host David Letterman, right, and comic Jay Thomas get ready to throw footballs at the Late Show Christmas tree during the annual Late Show Holiday Quarterback Challenge on the set of "Late Show with David Letterman," airing Thursday, Dec. 23, 2011 on the CBS Television Network. Thomas and Letterman each take turns tossing footballs at the Late Show Christmas tree to try and knock off the giant meatball perched at its top. (AP Photo/CBS, John Paul Filo)