 In the 1990s, spec scripts were widely used in television, wherein unexperienced writers could write a teleplay for their favorite shows. The X-Files had a large staff of writers, however occasionally to fill the large amount of ordered episodes per season, the staff would have to take a risk on a teleplay written by a freelance writer. "Sanguinarium" was such a case, being written by sisters Vivian Mayhew and Valerie Mayhew, their first experience with writing a one-hour network program. They would later be responsible for several episodes in the television series Charmed. The sisters asked staff writers Glen Morgan and James Wong for suggestions. Morgan and Wong stated that "the scariest things are those which repeat every day". After Vivian was paged by a number she did not know, she concluded that a pager qualified as a scary thing because an unknown person could connect with its owner. Then the Mayhews went from the pagers to a class that normally uses them, doctors, and concluded that doctors losing control and being bewitched could be a good plot. After writing the spec script, they presented them to Morgan and Wong, who suggested they change the villain from a woman to a man as "plastic surgery is related to vanity, and everyone expects that from a woman, but not a man." The spec script written by the Mayhew sisters was chosen to become a full episode. "Sanguinarium" stands as the siblings' only work in The X-Files.
