Frohike tells Mulder that Christina Sherman gave birth to a girl on September 25, 1994. In real life, this was the date of birth of Gillian Anderson's daughter Piper Anderson-Klotz.
The young actress Mecca Menard who originally played Emily was terrified of the hospital setting, and as a result the producers had to recast the role and re-shoot all footage featuring the little girl. Despite the deleted scenes Mecca is in all the promotional photos of Christmas Carol. A few years later she played young Natalie in Millennium (1996) (also created by Chris Carter).
The old man that Dr. Caulderon shape-shifts into when Scully is chasing him down the hospital corridor is the same actor that Jeremiah Smith shape-shifts into on the video footage in Talitha Cumi (1996).