Glen Morgan and James Wong's early influence on "The X-Files" mythology led to their introduction of popular secondary characters who continued for years in episodes written by others: Scully's father, William (Don S. Davis); her mother, Margaret (Sheila Larken); and her sister, Melissa (Melinda McGraw). The conspiracy-inspired trio The Lone Gunmen were also secondary characters. The trio was introduced in the first-season episode "E.B.E." as a way to make Mulder appear more credible. They were originally meant to appear in only that episode, but due to their popularity, they returned in the second-season episode "Blood" and became recurring characters. Cigarette Smoking Man portrayed by William B. Davis, was initially cast as an extra in the pilot episode. His character, however, grew into the main antagonist.