The Exorcist was a popular book and movie on Earth about demonic possession.
The Exorcist is a 1971 novel by American writer William Peter Blatty. In 1973, the novel was adapted by Blatty for the film of the same name.
When Cassandra Fraiser was becoming a Hok'tar in 2001, Major Samantha Carter said that until her "head starts spinning around, and probably even then," Carter would still see Cassandra as herself. (SG1: "Rite of Passage")