It's a big TV world, with something for almost anyone, but I'm sure there are shows you regularly flick past, thinking ''You mean that's still on?'' You know what I'm referring to: sitcoms whose comedy evaporated immediately after their pilot episodes; shows that seem so threadbare of quality, it's amazing they get renewed year after year. For me, three prime stumpers, a trio of lucky ducks, are Coach, Dave's World, and Wings.
Coach, now in its eighth season of jerry-built jock jokes, is foremost among inexplicable sitcom successes. Oh, sure, as Hayden Fox, currently coach of the pro football team the Orlando Breakers, Craig T. Nelson does exude effortless conviction he's got the tidy bulk and easygoing swagger of a middle-aged athlete. And his costar Shelley Fabares, as Hayden's wife, Christine, is both charming and a bona fide baby-boomer icon for her role as the eldest daughter in The Donna Reed Show as well as for her incandescent 1962 pop hit, ''Johnny Angel.''
But the show's two locker-room dumbbells, Luther (Jerry Van Dyke) and Dauber (Bill Fagerbakke), used up whatever nutball appeal they had long ago. And even Nelson looks as if he's just going through the motions, just racking up episodes for those big syndication bucks. Coach was never good for major laughs it's comfort television, the kind of thing people watch simply to be with characters they like. But these days, the Coach crew are loud, boring guests in our living room. D