Jimmy Fallon channeled his inner Michael Jackson the other night, stunning the casts of “30 Rock,” “Saturday Night Live” and his own show when he moonwalked across the stage and broke into a rousing rendition of “Billy Jean” and “Man in the Mirror” at the multicast holiday party at the Players Club. Even caterer Andrea Correale stopped what she was doing to watch the show, which was met with a rousing ovation by “SNL” honcho Lorne Michaels and “30 Rock” star Jack McBrayer.