Maude Flanders (ghost)

Maude Flanders' ghost is the spirit of Ned's dead wife.

Biography
The Simpsons and Ned hold a seance in order to contact Ned's dead wife Maude. While praying, Bart comes in dressed as Maude's ghost and finds out that Maude's real ghost is behind him, which startles everyone. Homer and Ned admire Maude, but they're terrified when she turns into a hideous ghoul, with the exception of Lisa who isn't afraid of her because of her scepticism.

In the future, Maude's ghost marries Ned after Homer accidentally kills Edna Krabappel. She isn't evil at all and she says there is no God, with Heaven being "an empty meaningless void".