There is a particular clock that shows up in almost every episode.
An important aspect of the show's Musik is classic rock, most of which comes from creator Eric Kripke's own record collection, although one of his Favorit bands - Led Zeppelin - has always been too expensive to license.
The role of Ruby was written for Kristen Bell. But she turned it down, Katie Cassidy was cast instead.
Jim Beaver's character (Bobby) was only supposed to make a one-time appearance.
While it maybe coincidental the choice of the name Winchester for the family is interesting. There is a rather famous mansion in California built Von Sarah Winchester, wife of the gun magnate, which was under constant construction for 38 years for paranormal reasons. According to legend the reason for the constant building was a medium telling Mrs. Winchester that if she ever stopped building the spirits of those killed Von Winchester rifles would come after her. The strange Design of the mansion is also attributed to this. It was built with dead ends and stairs to nowhere allegedly to confuse spirits.
The characters Alastair and Crowley pay homage to notorious occultist Aleister Crowley.