Gerti – played by Cathy Moriarty, is the raspy, tow-headed leader of the witch coven in Casper Meets Wendy. She is apparently based on Thelma from the Harvey Comics stories.
The only intelligent member of the clan, she has to put up with her two idiotic sisters and her sweet natured niece Wendy the Good Little Witch. She is shown to be the leader of her family in most situations especially when it comes to Wendy. She has the power to transfigure humans into animals from a distance by firing a yellow light from her fingertips, and is the primary magic user. It is her knowledge of famous witches and wizards that gets her into situations like hiding from her enemies. Gerti, or Gert as she tends to be called, has a tendency to be rather strict but every once in a while shows her soft spot and love for her niece. She is also very sensitive about anything that is considered “ugly” by a witch's standards, like the interior of the Sunny Bright Resort. She forgives the Ghostly Trio in the climax of the film.
Cathy Moriarty, who plays Gerti, also played Carrigan Crittenden in Casper (1995).