Fridays in December have been devoted to the films of Myrna Loy, so it’s mere coincidence that, if I note that this last Friday night before Christmas is a thin night for TV viewing, the word Thin has a double meaning. Six Thin Man movies starring William Powell and Myrna Loy as classy married sleuths Nick and Nora Charles, are shown tonight on TCM, starting at 8 p.m. ET with 1934’s original The Thin Man.