The character Colonel Claus Von Stiffenberg is named in reference to Claus von Stauffenberg, a German army officer most famous for his failed assassination attempt of Adolf Hitler on July 20, 1944. Similarly, the speech that he gives as the Zombies declare war on the other factions is a reference to "Ich bin ein Berliner" (translated to "I am a Berliner"), a speech given by U.S. President John F. Kennedy during the Cold War, specifically the line "All free men, wherever they may live, are citizens of Berlin, and therefore, as a free man, I take pride in the words "Ich bin ein Berliner!"".