Aggie Cromwell is a fictional character from the Disney Channel movie series, Halloweentown. She is portrayed as a powerful and wise witch who is the grandmother of the main character, Marnie Piper. Aggie plays a crucial role in guiding her family and helping them understand their magical heritage. In the films, Aggie is known for her vibrant personality and her commitment to protecting the magical world of Halloweentown. She often uses her magic to assist her family and friends, showcasing her strong connection to both the human and magical realms.