At the beginning, Scully sings Three Dog Night's "Joy to the World" to her son, William. This is the second time in the series Scully has sung and has sung that particular song. The other was in Detour (1997), in which she sings it to Mulder in the middle of the woods.
Maggie Wheeler, former girlfriend of David Duchovny, returned to the series, singing the lullaby at the end of the episode.
When the mystery character sneaks out of the room he is staying in and then goes to William's, the camera pans across and stops in front of a fish tank. That is the same aquarium that was in Mulder's apartment seen in the earlier episodes.
In the Paley Center 20-anniversary interview hosted in 2013, David Duchovny confessed he doesn't feel much connected to this episode, his third as director, because it was more plot-driven than his previous episodes.