The Witch Sisters are known as (Gert, Gabby and Fanny) are three witches who were always using their magic powers to do wicked things unlike their niece Wendy the Good Little Witch who is the female/witch equivalent to Casper. In both the Casper and Wendy comics, the Witch Sisters are named Thelma, Velma and Zelma, who are three ugly old hags with green skin and warts on their face, unlike their 1998 direct-to-video film counterpart in Casper Meets Wendy, where the Witch Sisters look normal except when they are wearing their witch's gown.
In Casper Meets Wendy, Desmond Spellman, an evil warlock tries to destroy Wendy and the Witch Sisters after hearing Wendy is a more greater witch. Wendy and the Witch Sisters had to try to stop using magic so they wouldn't get caught.
The lead Witch Sisters, Gert is portrayed by Cathy Moriarty who also appeared in the 1995 feature film, Casper, as the film's antagonist: Carrigan Crittenden.
In the comics, Wendy Witch World, and Casper Meets Wendy, Wendy and the Witch Sisters lived in a cottage in a haunted forest, where most stereotypical witches would be thought to live in.
Gert has yellow magic, Gabby has blue magic and Fanny has orange magic.