And I totally found two things that tye those shows together! John, the Brothers Dean's dad? He was totally a Marine. Also, spontaneous human combustion (yeah, I realize "Heart Break" wasn't actual human combustion, but it still counts)!
Also, on the website for Supernatural (http://supernatural.warnerbros.com/)? They've got 'wraiths' listed in their glossary/encycolpedia type section:
A Scottish word, first used in English in 1513. A wraith is an apparition, vision, or double of another living person. Its appearance is commonly seen as an omen that the person being doubled is about to die.
I KNEW the guy who swooped them up was Fake!Dad!