Carol Burnett is joining "Glee" as Sue Sylvester's semi-oft-heard-of-never-seen mother, who is also a Nazi hunter. (There must be a story in there somewhere ... We'll find out what it is.)  Of course, if the brilliant Harvey Korman were still alive -- sadly, he died a couple of years ago -- he would be cast as Sue's father. This scoop courtesy of the always-reliable Michael Ausiello at EW, by the way. How great an idea is Burnett for the role? Reasonably great. Burnett's hardly been in the TV witness-protection program -- there have been extended cameos on "SVU" and "Desperate  Housewives."  And let's not forget the ABC revival of "Once Upon a Mattress." Theoretically, "Glee" could turn into her seventh (or would it be eighth, or ninth?) Emmy: She can, of course, sing and dance.