The brand of cigarettes that Mrs. Martinez smokes, Morley, is not a real brand, but it has been a popular fake cigarette brand in TV shows and movies since 1960, when it appeared in Alfred Hitchcock's movie Psycho (1960). Perhaps its best-known use was as the brand preferred by the "Cigarette Smoking Man" on The X-Files (1993).
John Hurt portrayed Abraham Setrakian in the original pilot. Due to other commitments, he was unable to continue in the role.
Based on the first of a trilogy of books written by both Guillermo del Toro and Chuck Hogan. The second book is The Fall and the trilogy concludes with The Night Eternal.
Although featured as the secondary antagonist of the series, the character of Thomas Eichorst was largely an original creation for the show. In the novels, Eichorst is a minor henchman and largely inconsequential character who appears only briefly in the second book.