Anyone fluent in German who also is aware of a little about Werner von Braun, who designed the V1 and V2 rockets made use of to blitz England in 1944-45 and went on to direct the American room race, will acknowledge the x-Stoff references as shorthand for the numerous lethal elements of wartime German rocket fuels. Sheldon when a "terrifying" music chicken flies by means of the apartment window and lands on his couch house.