Pazuzu is a demon 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, which was then delivered via Amazon to the Simpson house by Homer, who thought it was pizza. It was put in Maggie's room and Pazuzu's soul came out of the statue and possessed Maggie, turning her into an evil demon, who terrorized everyone at the house party. Marge hired an Irish Priest to come and banish Pazuzu from her body. He did just that, but instantly afterwards, Pazuzu possessed Bart (though Pazuzu would come to regret that possession due to Bart's soul being too dark and evil even for the 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.