For their rescue scene, David Duchovny and Gillian Anderson spent most of a day in pits covered in mud and yellow sludge. Fortunately, they were both wearing wetsuits underneath their costumes.
The sludge that engulfs Mulder and Scully was made from a food thickener with a hefty dose of yellow food coloring.
Scully talks about huge fungal organisms that are dozens of square feet and hundreds of tons in size having a precedent in nature. The largest one known to exist was discovered in 1998, about a year before this episode aired, in the Blue Mountains of Northeastern Oregon. This particular organism is a fungus called Armillaria ostoyae, and it feeds off the roots of pine and fir trees. It extends filaments between root wads as it grows forming one massive organism. This particular one occupies some 2,384 acres of soil, which is equal to about four-square miles; it is estimated to weigh over 10,000 tons and is at least 2,400 years old. Some scientists think it could be as old as 8,000 years. DNA testing was used to confirm it is in fact one single massive fungal organism and not a bunch of smaller ones growing together.
This is the second episode in a row to involve psychoactive drugs, Scully gets stoned again. The previous week involved a synthetic drug used for brainwashing and suggestion control.
Stars "Supernatural" legend Jim Beaver aka "Bobby Singer"!