WBGhiro: Are you sure it's a reference to Apocalipse Now! though? yeah it fits
well, but i could swear i've heard the exact line "the horror, the horror" somewhere before.
nondeplumage: The horror...the horror...are the last words of the antagonist in the novel
Apocalypse Now is based on,
Heart of Darkness. That's where it originally comes from, and when it's used elsewhere it's usually a direct rip off of the film or book, especially when it's a comedy. Originally I remembered it wrong and thought it was the pony laying on her back who said it, which is why I thought it was off of the film.
But it's such a famous line that it's hard to imagine just being thought up by the writers without knowing where it came from.
It wasn't from either of those things. It's funny how you don't know shit about books or film.