Absentee Actor: Mulder is completely absent from the episode: David Duchovny was busy promoting the film Playing God, which had just been released. The absence isn't glaring because Scully is on vacation from work and visiting her family for Christmas.
Happy Flashback: Scully reminisces about her past Christmas. Teenage Melissa and she go peeking at their presents. Their mum comes to them as well and the girls open together their golden crosses.
Supernatural Phone: Scully receives a phone call from a mysterious woman who sounds just like her dead sister Melissa. She urges her to help a little girl who turns out to be Scully's biological daughter. The FBI were able to trace the address and it's confirmed that a call came in from that place, but there was no outgoing call from that residence and their phone had been off the hook.
Phone Call from the Dead: Scully gets a phone call from her dead sister. This ends up leading her to a girl who is her biological daughter, created using the ovum extracted from her body.
Present Peeking: Teenage Melissa and Dana go to the tree to peek at their presents at night.
Real-Life Relative: Gillian Anderson's little sister Zoe plays Scully's teenage self in the flashback.