Every episode of the show is named after a famous song. "I Will Follow You Into the Dark" is a song by Death Cab for Cutie.
Cristina: Hunt won't even look at me without going all Apocalypse Now on me this morning.
Apocalypse Now is the 1979 movie directed by Francis Ford Coppola where Martin Sheen as Captain Willard is sent on a dangerous mission into Cambodia to assassinate a renegade Green Beret who has set himself up as a god for a local tribe.