Originally, the script called for Banton's shadow to be able to move independently, but Chris Carter scrapped the idea.
As Mulder and Scully are investigating the first crime scene, Scully inspects the heat register. The local detective says, "You don't think anyone could have squeezed in there?" To which Scully replies, "You never know." Obviously a reference to their arch-nemesis from Season 1 Eugene Victor Tooms, who could change his shape to fit through air vents and ducts.
Kate Twa, who plays Kelly Ryan, previously appeared in Gender Bender (1994), playing the female half of the gender-switching serial killer.
Vince Gilligan was originally a fan of the series. He wrote a script and sent it to Fox. This script became this episode.