First time Dean Winchester has called Sam Winchester "Samuel".
This episode was filmed very differently to any other episodes. Usually for car scenes there's a rig for cameras and a trailer that pulls the car for closeups because the actors can't see to drive. For this episode the crew actually rigged the cameras into and onto the car in a way that Jensen Ackles could still see enough to drive, they would rig the lights and roll sound and then the actors would literally just drive away from the crew up the road. Ackles and Jared Padalecki have said it was weird because they were just on their own with no one to say "action" or "cut", and it was up to them to do most of their scenes without those cues.
This is the first and only episode to have no soundtrack. All the music in the episode can be heard from Sam, Dean, and/or Baby's point of view, such as Dean's tapes in the Impala, music in the bunker's garage, or music coming from the roadhouse.
The whole episode takes place inside the Impala. This concept of restricting the show to a limited premise is known as "bottle necking" the episode.
The first episode in over 10 seasons of Supernatural where the only music ever heard is music which the characters themselves can hear. The term for this is "diegetic" music, as opposed to "non-diegetic" music, which is the normal soundtrack music heard throughout the rest of the series.