Quarantine "yellow jack" but this was also a name for yellow fever, which probably derives its common name from the flag, not the color of the victims (cholera ships also used a yellow flag). The plain yellow flag ("Quebec" or Q in international maritime signal flags) probably derives its letter symbol for its initial use in "quarantine", but this flag in modern times indicates the opposite—a ship that declares itself free of quarantinable disease, and requests boarding and routine port inspection. Australia has perhaps the world's strictest quarantine standards. Quarantine in northern Australia is important because of its proximity to South-east
What Is and What Should Never Be (Supernatural) deceased girlfriend—but she was busy filming for the Texas-based television series "Friday Night Lights". Because Jessica was an integral aspect of the storyline, the production schedule was adjusted to accommodate the actress. The first five days of filming commenced for "What Is and What Should Never Be", and production then shifted to "All Hell Breaks Loose, Part One" until Palicki became available for the final three days of filming. However, she was not present for filming of the episode's climax. Instead, the actress filmed her part in front of a blue screen, and was later digitally added into the scene.