Chad Lindbergs character Ash tells Dean and Sam that he was kicked from MIT for fighting, this is the 2nd time he has played a character that he has been to MIT and left (the fast and the furious 1), this could be a direct reference to his character Jesse.
The trivia items below may give away important plot points.
This episode marks the very first appearance of what the crew of Supernatural affectionately calls Jensen Ackles' "one perfect tear" (the fandom sometimes calls it the "single man-tear", as referenced in 10.5 "Fan Fiction"). When Sam and Dean are burning John's body, Sam is full on crying, tears streaming down his face, whereas Dean is handling it more stoically until just before the scene fades out, when a single tear falls. Jensen jokes that for some reason it's usually just the one tear and the focus puller gets excited and tends to focus right in on that "leaky eye". Indeed, the solitary tear tends to be the way that Dean cries, typically because it escapes while he's trying to hold the emotion in (with a few notable exceptions). This episode marks the first time we see Dean actually cry, though it's not the first time he's bean emotional.