Splendora Agatha "Aggie" Cromwell, portrayed by Debbie Reynolds as an older Aggie, Sara Paxton as a younger Aggie, is featured throughout the Halloweentown film series.
Aggie is the mother of Gwen Piper and grandmother of Marnie, Dylan, and Sophie Piper. She is the daughter of Merlin's cousin Marvin. It is unknown if Cromwell was her maiden name, or if she is widowed, as she is referred to by others as Mrs. Cromwell in Halloweentown High. She is a witch and resides in Halloweentown until Gwen offers to let her move to the human world and live with them at the end of the first movie. She agrees but is having a very hard time not using her magic. In the first two movies, she carries a bottomless carpetbag that magically strolls along next to her as she walks. The carpet bag is very faithful to her as well as being slightly cowardly, as in the first movie it is scared to jump off a flying bus, but does so when she pretends to leave without it.
In Halloweentown High, she tries to fit in by taking various teaching jobs at Marnie and Dylan's high school and falls for the principal. She has a new bag that follows her around, this one resembling an alligator without a head that loves to eat.
In Return to Halloweentown, it is revealed that during the dark times, Splendora Agatha Cromwell was the Princess of Halloweentown, who possessed the Gift, an ancient power. It was a necklace that had the power to give the wearer complete control over any person – but it could only be worn by a Cromwell witch or warlock. An evil battalion of dark warlocks and witches known as the Dominion sought the Gift and wanted Splendora to use it to dominate Halloweentown. Wanting to live like a regular witch, Splendora placed the Gift in a locked box and buried it under the ruins of Cromwell Castle - where Witch University currently sits. It is said that only her heir could unleash the Gift that's stored inside and use the power within it.