The first appearance of Chuck Burk, Mulder's go-to guy for all things related to digital imaging.
The only X Files episode rated '18' in the U.K. by the BBFC.
The hospital staircase, where Scully and Mulder are standing towards the end of the episode, is the same staircase from the Supernatural (2005) episode In My Time of Dying (2006) (season 2, episode 1).