Character mistake: When Josh is giving his WWII example to Donna, he talks about "France, Austria and England being pounded by the Germans." Except Austria was incorporated into the Third Reich after the Anschluss of 1938; it was essentially part of Germany for all intents and purposes. It therefore was not being attacked by the Germans at all. One would have thought Josh, who shows a firm grasp of WWII information in other episodes, would have known this.
Character mistake: In this episode the Organisation of Cartographers for Social Equality claims the cartographer Mercator is German. He is in fact Belgian. He was born Rupelmonde Belgium, March 5, 1512 and died at Duisburg Germany, December 2nd, 1594.