Gwendolyn "Gwen" Piper (née Cromwell), played by Judith Hoag, appears throughout the Halloweentown film series.
Gwen is the daughter of Aggie Cromwell. She is the mother of Marnie, Dylan, Sophie Piper. She was born as a witch in Halloweentown. When she was young, she dated Kalabar, and she also went on a date with the boogeyman. She gave up her magical heritage for William Piper (a mortal) and married him. Even after her husband was deceased, she continues to live in the mortal world, believing that it is better to be "normal" and hates Halloween. Since Halloweentown Gwen uses her magic more freely and it continues to grow with each film.
In the film Halloweentown, she keeps the town Halloweentown a secret from her children and would prefer to raise them as a mortal, not allowing anything that has to do with magic or Halloween be mentioned in the house. Dylan agrees with her, but Marnie and Sophie do not like that. Gwen would often fight with her mother on the subject of whether or not she should allow her children to follow their family's tradition, especially Marnie, who is about to lose her powers forever after her 13th Halloween. At the end of the first film, she offers to let Aggie come live with them and agrees to have Marnie do her witch training. Although Gwen accepts her child's urge to connect more with the magical heritage, she continues to encourage Marnie to not let all that magic go to her head. Though Gwen eventually begins to accept magic more and more through each film.
In Halloweentown II: Kalabar's Revenge, Gwen meets a handsome single father named Alex but doesn't know that he is actually a golem created to lure her into a trap. He takes her to a Halloween party, where the warlock Kal turns her and everyone at the party into monsters. By combining their magic, her family manages to reverse the spell.
In Halloweentown High, she helps Marnie joggle nine teenage kids of different mythical heritage. When they discover that someone is trying to steal their magic by failing Marnie's project, Gwen teleports herself to Halloweentown to find proof for the Halloweentown Council. In the end, Gwen rescues Cassie from her prison and returns to the mortal world in time to help stop the plot.
In Return to Halloweentown, her children flew off for college and witch training, and she became a real estate agent and used magic to make the houses look better. When Dylan gets turned into a dog, Marnie calls for her help. She, Marnie, and Dylan combine their magic and "destroy" the Gift together.