But, all along — and long after the series had gone into syndication, and years of reruns — there was a hidden joke in “Hogan’s Heroes.” It was simply this. Many of its characters were played by Jewish refugees from the Nazis. Consider: Colonel Wilhelm Klink, the commandant of the stalag. His chief characteristics: vanity, insecurity, paranoia, and basically inept, in constant fear of being sent to the Russian front. He was played by Werner Klemperer, a veteran German entertainer. He was born into a family that was part of German-Jewish cultural aristocracy. His father was the renowned conductor Otto...