Chris Carter had to lobby hard for the casting of Brad Dourif as serial killer Luther Lee Boggs. Dourif was more expensive than the usual guest star but Carter knew he would be perfect for the role. He rang Fox president Peter Roth at his home on Thanksgiving to plead his case. Roth agreed to it, mainly because he wanted to get back to his dinner.
In the scene where he appears as a vision to his on-screen daughter, Don S. Davis is mouthing The Lord's Prayer.
Mulder addresses Scully as "Dana" while inquiring as to her well-being in their first scene. Presumably, because he heard of her father's death. She hesitates and mouths her name to herself before responding "fine". The agents had been exclusively on "last name basis" up until this point.