The only Christmas episode in the show's run.
Giles mocks his book's description of the Bringers with the following line: "They're rebels and they'll never, ever be any good." This is a reference to the song "He's a Rebel" by the 60's band, The Crystals.
They eyeless "Bringers" in black robes, which return in Season 7, are a nod to The Devil's Rain (1975) which features acolytes of a satanic cult in the same look.
Reveals the real reason Angel was brought back from the Hell universe.
The flashback scenes take place in Dublin on December 25, 1838 and London on December 25, 1883.