Ms. Grunkle is the villainess in the computer game "Jumpstart Adventures 4th Grade" and the fourth-grade substitute teacher who turned the kids into monsters and brought them to Haunted Island, which she apparently rules over. Her appearance fits the popular depiction of a witch to a tee, with her having gray skin (although it's blue on the icon), black clothing and a pointed hat. Presumably, she was voiced by Jeannie Elias, since Elias was the only female voice actor credited.
Ms. Grunkle appears at the beginning and ending of the game as well as whenever the user enters a new room in her house. Sometime after you finish playing one of the minigames she flies by on her broomstick to taunt the user with typical villainous comments ("So, you think you're pretty good at my little games? Well, you haven't seen anything yet!") before flying off. Curiously, she is sometimes referred to as "Mrs. Grunkle," prompting one to wonder whatever became of husband (she has a skeleton in her living room watching TV and holding a remote, which could have been her husband at one point). She does not have an explained motivation for her actions in the game.