This is one of only two episodes in season 6 that Drew Fuller (Chris) did not appear in. The other one is episode #8 'Sword and the City'.
Eric Dane and Balthazar Getty are best friends in real life. Though both have guest starred in several episodes, this is the only episode they're both in and share a scene.
The Swarm Demons' entry in The Book of Shadows reads, "Distant cousins of Kazis and Vampires. The demonic hive of evil known as Swarm Demons are pack hunters of the Underworld. The Swarm Drones follow the orders of their King without question and often sacrifice themselves for the good of the collective body.".
The Aura Cleanse spell reads, "I call to thee, pure Witches fire, Through vortex flow the heavenly mire, Cleanse brackish karma of debris, From dark to light sweep history...".
The title is a play on words using the expression "Used Cars".