In the grand tradition of the Dancing Santa comes Big Mouth Billy Bass, a faux-wood-mounted rubber fish that sings along to such ditties as ”Take Me to the River” and ”Don’t Worry, Be Happy” while swiveling its head and fixing its fishy gaze on listeners. Initially marketed to the fisherman demo (who knew?) when it was introduced in February by the Irving, Tex.-based Gemmy Industries, Inc., the tail-flapping novelty sold so swimmingly, it’s now available for about $25 everywhere from sports to toy stores. ”It has taken off past our wildest expectations,” says Gemmy sales and marketing VP Jim Van Den Dyssel. Coming soon: a rapping catfish, a rocking trout, and a 25th anniversary Jaws tie-in featuring a great white crooning ”Mack the Knife.” Talk about reeling ’em in.