Pazuzu is a demonic being depicted in ancient Mesopotamian religion. He is portrayed as the king of the demons of the wind, brother of Humbaba and son of the god Hanbi. He also represented the southwestern wind, the bearer of storms and drought.
In the "Treehouse of Horror XXVIII" segment "The Exor-Sis", a statue of Pazuzu was discovered in a pre-Christian temple site in Northern Iraq, and then delivered via Amazon to the Simpson house by Homer, who ordered the statue, thinking that it was pizza. It was put in Maggie's room as a decoration, and Pazuzu's soul came out of the statue and possessed Maggie, turning her into an evil demon, who terrorized the house party and killed several people (Helen Lovejoy, Dr. Hibbert, and Ned Flanders). Marge hired an Irish Catholic priest to banish Pazuzu from Maggie's body. He did but then Pazuzu quickly possessed Bart, soon coming to regret it as Bart's soul is too dark and evil even for the horrible demon.
In the next segment of the same Treehouse of Horror episode, "Coralisa", Maggie still had some of Pazuzu's evil left in her, causing her to vomit all over the kitchen table.