Cutshaw and the Ninth Configuration/Exorc ist Connection
One often hears that "Ninth Configuration" is a sequel to "Exorcist" that uses a minor character (the astronaut Cutshaw) as the protagonist. In fact, the imdb trivia note says just that. This version of the story doesn't make much sense since Blatty wrote "Twinkle Twinkle Killer Kane" several years before he wrote "The Exorcist." If the astronaut at the MacNeil party is Cutshaw, then it's a case of a main character from the earlier novel "Kane" having a minor appearance in a the Exorcist rather than the reverse, even though "Ninth Configuration" was a later film.
Furthermore, is the astronaut in "Exorcist" ever called Cutshaw? He isn't in the film - what about the book?