Arthur's Christmas was a  difficult to come up with a new spin on something as established as a  movie, but the animated "Arthur Christmas" does a good job of it.The film, cowritten and directed by Sarah Smith, imagines that Santa Claus is a position passed along the Claus line like royalty and sets out to explain how the fat old guy is able to deliver toys to kids the world over in a single night. All of that is interesting, of course, but the real draw of "Arthur Christmas" is simpler: It's really funny.