"Bobby Singer", friend of the family Dean seeks out for help, is a reference to executive producer Robert Singer.
The secluded cabin in the woods was actually built on stage. In the Supernatural: The Official Companion - Season 1, production designer Jerry Wanek explains that the location had to be particularly atmospheric because the Winchesters were going to spend a lot of time in it. So they had to build a forest and then the cabin.
Contrary to what other trivia in this section says, this is the only Season finale to NOT feature the song "Carry On Wayward Son" by Kansas. Instead, that song originally played over the montage in season 1 episode 21 (Salvation (2006)) and can be heard on the DVD. However when the series was made available on Netflix, Due to licencing issues, changes were made to the music used in season 1. "Carry On Wayward Son" was replaced in the original mintage of 1.21 by a song called "Penance/Murder" by composer Christopher Lennertz, who composes scores for Supernatural.
As Sam begins reading, Meg asks, "An exorcism? Are you serious?" To which Dean replies, "We're going for it, baby. Head spinning, projectile vomiting - the whole nine yards." He is referring to the horror classic The Exorcist (1973).