Celine Demon
From Super-wiki
The term Celine Demon was coined on the Television Without Pity boards on September 14, 2005, in a discussion after the airing of 1.01 Pilot and refers to the demon who killed the Winchester brothers' mother Mary Winchester and later Sam's girlfriend Jessica Moore (though in 5.20 The Devil You Know it was revealed that Brady - a college friend of Sam's possessed by a demon, is the one who killed Jess on Azazel's orders).
The name is derived from a misreading of the words "Ceiling Demon" as "Celine Dion" (Canadian pop singer) by TWOP-user thinkcwik. The singer's name and the nickname for the demon were meshed and the new term stuck.
Sam says that his favorite singer is Celine Dion in 14.20 Moriah.
