Denis Leary has signed on to star in Fox's six-part holiday comedy, A Moody Christmas."MerrySummerXmas," Leary tweeted Tuesday, along with a link to a story about the casting news.Fox also teased the December project on Twitter."Christmas came early! A Moody Christmas," the network said.Deadline.com reported the half-hour, single-camera show is an adaptation of an Australian series.This is not Leary's first holiday adventure. He also starred with Kevin Spacey in the 1994 dark comedy film, The Ref.His other credits include Animal Kingdom, Rescue Me, Sex & Drugs & Rock & Roll and the Ice Age film franchise.