Witch Marge

"That's right, I'm a witch. And I'm the one who withered your livestock, soured your sheep's milk and made your shirts itchy!"

~ Marge, revealing herself to the townfolk.
Witch Marge was Marge Simpson as a witch in the story "Easy Bake Coven", the final segment of Treehouse of Horror VIII.

"Easy-Bake Coven"
The segment takes place in Sprynge-field, 1649 where hysteria of witchcraft is an all time high. After burning Agnes Skinner and a few others at the stake for suspected witchcraft, the town decides who to accuse and kill next. When Marge tries to talk some sense into them, they immediately accuse her for being one and sentence her to due process. She is given no choice but to fall off a cliff: if shes innocent, she will die, but if she reallt is a witch, she would beheaded and Chief Wiggum shoves her off, much to her family's dismay. A few seconds later, Marge appears a witch, with black hair and green skin, shocking the townfolk. She reveals that she was behind everything the other women were accused of and swears revenge on the town. She turns Chief Wiggum into a giant gopher, Lou and Eddie into a fairy and snowman respectively, and before she flew off, she summoned a swarm of bats from her hair to scare the townfolk away

She flies into a cave high on a mountain, where her sisters, Patty and Selma Bouvier, who are also witches are brewing up dark magic. They spy on the town through their cauldron and overhear Ned and Maude Flanders talking about rumors of how witches eat children. The three witches decide its a good idea and go to the Flanders' house for Rod and Todd. Ned tries to scare them off with a cross but they don't even flinch. As they carry the Flanders' children away, Maude offers them gingerbread men instead and they agree. They go to other houses for children but end up being given candy instead. The witches then decide that every year on this night to go to people's houses for candy, and they fly away cackling. Their decision becomes the origin of Halloween night and trick-o-treating.

Trivia

 * The segment parodies Arthur Miller's play, The Crucible and the Salem Witch Trials that occurred in 1692.
 * Marge's appearance parodies The Wicked Witch of the West from The Wizard of Oz. 
 * She even parodies her cackling when she flys.