Writer-director Stuart Ross, creator of the phenomenally successful 1990 musical Forever Plaid, claims that he wrote this holiday-show sequel as a response to 9/11. Riiiight. Well, I suppose a sequel was inevitable. What’s remarkable is that Ross hasn’t lowered his standards. This show, like the earlier one, is pitched at a middle-class, middlebrow, late-late-middle-aged audience–the same people, judging by the material, who kept Ed Sullivan and Perry Como on the air for so many years. The jokes the Four Plaids tell are a little corny, but the singing is superb, with close harmonies so close they’re unearthly. There’s nothing surprising in these holiday standards, but they should raise a smile on even the sourest grinch’s face. Through 12/31: Tue 7:30 PM, Wed 1:30 and 7:30 PM, Thu 7:30 PM, Fri 8 PM, Sat 2:30 and 8 PM, Sun 2:30 and 7 PM, Wed 12/14, 1:30 and 7:30 PM, no show Tue 12/13, Drury Lane Theatre Water Tower Place, 175 E. Chestnut, 312-642-2000, $35-$48.