S3, E10: When Bobby (recurring guest star Jim Beaver) falls into a coma and can't be awakened, Sam and Dean race to his side. While unconscious, Bobby battles his personal demons, and it is revealed why he became a hunter. Sam and Dean discover someone poisoned Bobby with a potion that will kill him if he doesn't wake soon. The brothers decide to take the potion themselves to enter Bobby's dream and try to save him, and come face to face with their own personal nightmares.