Names this 'character' is known by both in fandom and canon:
- The Demon (all Winchesters refer to it thus in Season 1)
- The Yellow-Eyed Demon (Dean refers to it thus in Season 2)
- Celine Demon (a nickname used by the fans. See below for an etymology of this nickname)
- In a draft script for 2.02, Dean refers to it as the Big Bad.
- The Demon attacks families on the night the baby is exactly 6 months old. (Jess is the exception to this rule - Sam is 22 & 6 months old.)
- A week prior to the attack, the geographical area has cattle deaths, electrical storms and temperature fluctuations.
- It makes clocks stop, and electical devices go haywire.
- It is impervious to Holy Water
- Following what appears to be a surge of activity around the time Mary died (Max's mother was also killed around this time), the Demon was dormant until late 2005.
- It has yellow eyes (iris and pupil).
- It possesses human hosts, but can exist in a disembodied form also.
- Impervious to the salt barrier.
- It is vulnerable to the Colt.
The Demon's Children
- Possess human hosts, are able to animate the human body it is possessing even if the body sustains mortal injury.
- Eyes turn entirely black during possession, though this can seemingly be turned on and off.
- They are impervious to hallowed ground ("that may work in the minor league, but not with me" - Meg, Salvation), but not to Holy Water.
- They can be exorcised and thus destroyed.
- Possession can occur by physical contact.
- Restricted by the salt barrier.
- Vulnerable to the Colt.
Etymology of the "Celine Demon" nickname
The term Celine Demon has been coined on the TWOP boards on September 14th, 2005, in a discussion after the airing of the 1.01 Pilot (episode) and means the demon, who killed the Winchester brothers' mother Mary Winchester.
It derived from a misreading of the words Ceiling Demon as Celine Dion (Canadian popsinger) by TWOP-user thinkcwik. The singer's name and the nickname for the demon were meshed and the new term stuck.