Evil!Sam is the name given by fans to Sam when he was possessed by the demon Meg in 2.14 Born Under a Bad Sign. Over time the term has come to have a broader use, particularly as a genre of fanfic, related to the following canonical ideas:
- That Sam had the potential to become evil, as suggested by John when he tells Dean in 2.01 In My Time of Dying that he might have to kill Sam.
- That Sam has something demonic within him. This had been hinted at through Sam being one of the Special Children and the idea further supported in 2.22 All Hell Breaks Loose: Part Two, when Azazel shows Sam a flashback to the night of the nursery fire that killed Mary, when Azazel is seen feeding his blood to the infant Sam.
- Azazel tells Dean that when Sam came back from the dead, through Dean's deal with the crossroads demon, he may have come back 'not quite Sam.'
- References in season 3 by demons to the fact that Sam had been chosen to be the leader of a demon army. In 3.01 The Magnificent Seven, the demon Pride refers to him as the "Boy King."
- Gordon Walker's repeated assertion that "Sam Winchester is the Antichrist."
- It gained wide currency in season 4 with Sam's alliance with Ruby, the use of his powers and the drinking of demon blood.
- In season 6, soulless Sam seemed a bit evil, but was generally referred to as RoboSam.
- sammmessiah community on LJ dedicated to "the quasi cult of Sam is my Demon Jesus"