Multi-hyphenate Christopher Guest  is gathering his hordes of improv comedy legends once again -- this time for the small screen.

Fred Willard, Michael McKean and Ed Begley Jr. are all joining Christopher Guest's upcoming HBO comedy series "Family Tree," according to The Hollywood Reporter.

Guest is teaming with "Bridesmaids" star Chris O'Dowd on the comedy, which centers on Tom Chadwick (O’Dowd), an unemployed thirtysomething who inherits a mysterious box from his hitherto unknown great aunt. The box's strange contents lead him to explore his family legacy, introducing him to all sorts of odd familial characters. 

McKean will play Tom's father while Begley is set to play Tom's Uncle Andy, who has an eccentric neighbor named Mike (Willard). Don Lake will also appear as a series regular.

Like Guest's features "Waiting For Guffman," "Best in Show" and "A Mighty Wind," the series will be shot in a faux documentary stye.

All four actors are regulars in Guest's acclaimed films.

"Family Tree" was picked up straight to series by HBO earlier this year. It will premiere sometime in 2013.