This 53-minute, 1970 animated film may be the most delightful of those sundry, stop-motion animated Christmas perennials that show up on television during the holidays. The clay animation production, boasting a wonderful musical score and art direction that occasionally underscores the flower-power era in which it was born, tells the story of Santa's origins, in which Kris Kringle decides to get toys into the hands of poor children in gloomy Sombertown. Charmingly narrated by Fred Astaire and featuring voices by Mickey Rooney and Keenan Wynn, Santa Claus Is Coming to Town presents a nice bridge between two generations of entertainment, the classic and the hip