List of Mystical Creatures in the Simpsons. They count as holiday spirits and religious creatures.
GodGod, voiced by Harry Shearer, has had many appearances in the series, including "Homer the Heretic", "Thank God It's Doomsday", and a quick scene with him, Buddha, and Colonel Sanders in "Pray Anything". He is portrayed in the traditional depiction of the Abrahamitic God in the Western world: a gray-haired Caucasian man in a white robe with a booming voice (though it is revealed in "A Star is Burns" that he speaks in "Flanderese", responding to Ned Flanders' "Thanks, God!" with "Okely-dokely!"). His face is only seen in a picture owned by Homer in "Pray Anything" (though this was likely an artist's depiction), a picture owned by Ned Flanders in "Alone Again, Natura-Diddily" and the opening sequence for "Treehouse of Horror XVI". In all other episodes, only his beard is seen. His body is usually surrounded by a glowing light, though not always. He doesn't seem to be all-knowing; for instance, when referring to his son, he stated that he didn't know "what you people did to him" but "He hasn't been the same since". One of his most distinctive features is that he is the only Simpsons character to be drawn with five fingers on each hand and five toes on each foot, though not always. There have been scenes where God has only 4 fingers like everyone else in the show.
DeathIn the 'Reaper Madness' segment of "Treehouse of Horror XIV", Death comes for Bart. After a comical around-the-house chase (Yakety Sax is played as background music), Homer kills Death (in revenge for "Snowball I and JFK") with a bowling ball. After dumping the bones in the trash, Homer tries on Death's robe. The flesh of his arm quickly rots away as he realises that he has become the new Grim Reaper. Homer soon becomes used to being Death and having a skeletal appendage that, when touching people, kills them. He is sent to claim the life of Jasper, one of the residents at the Springfield Retirement Castle. When he sees that Homer has filled the position, the old man inquires, "Where's the regular guy? Where's Doug?" Homer informs Jasper that he has taken over for him, to which Jasper wistfully replies "Aw, I liked Doug." Homer then kills him.
Jesus appeared in heaven in Thank God It's Doomsday. All he does is sit on a swing. Jesus also appeared in Mobile Homer when he's seen telling the Flanders to go to sleep when the r.v fumes come through the window. He appeared in She Used to Be My Girl in Heaven with SpongeBob SquarePants and Buddha and in Replaceable You whilst dancing with Mrs. Glick in Heaven.
The Devil first appeared in Bart Gets Hit by a Car in Bart's hallucination of heaven when Bart imagines himself in hell. In Homer vs. Lisa and the 8th Commandment the devil appeared in The Simpsons Home in Lisa's imagination of the family going to hell. In Treehouse of Horror XII Homer is sent to hell after he is rejected from heaven after dying of eating bad broccoli and not doing one good deed. In Treehouse of Horror IV Ned Flanders is in the guise of The Devil and turns into an actual one after Homer angers him. In Treehouse of Horror XVIII Ned Flanders is said to be a devil again. In Whacking Day Homer imagines an evil version of himself dressed up as the devil. A creepier taller devil appears in Treehouse of Horror XI when Homer goes to hell at the end of the first segment.