Walter Skinner's debut appearance.
The bile-like substance coating Tooms and his nest was actually yellow piping gel, which stuck to the cast members' skin and pulled out hair upon removal.
For his final scenes, Doug Hutchison performed nude. As scripted, Tooms was supposed to emerge from his "cocoon" wearing his animal control uniform, but Hutchison thought that made no sense.
When Scully calls him Fox, it is learned that Mulder does not like his first name, even having his parents call him Mulder.