Ad jokes in sitcoms: classic or crutch?

I’m beginning to think advertising jokes are the crutch of dying TV comedies. Consider NBC’s Scrubs, which until this season was one of my favorite shows. For three weeks running, the show has referenced TV ads in its scripts, first with a mock “The More You Know” PSA that paled in comparison to The Office’s April Fools’ spots, then with a parody of the classic ’80s drug-awareness PSA featuring a mustachioed, cokehead dad and the melodramatic line, “I learned it by watching you!” This week, Zach Braff’s J.D.