At the Halloween party, Dean introduces himself as FBI agent Seger, a possible nod to Bob Seger. Seger is an accomplished songwriter and rock legend inducted into the Rock and Roll Hall of Fame in 2004.
When introducing themselves to the pottery teacher, the brothers introduce themselves as Agent Geddy and Agent Lee. Geddy Lee is a Canadian musician and songwriter, best known as the lead vocalist, bassist, and keyboardist for the Canadian rock group Rush
"Samhain" is pronounced correctly in this episode. The character is a nod to Sam Hain from an episode of The Real Ghostbusters, "When Halloween Was Forever", in which the ghost of Halloween is summoned during a ritual and the creatures of the night "follow him around like the Pied Piper", as Sam says. (The inspiration for the RGB Sam Hain came from a God/demon of Halloween in Ray Bradbury's book "The Halloween Tree".
The trivia items below may give away important plot points.
FUTURE EPISODE SPOILERS: Kristen Robek plays Mrs Wallace in this episode (the wife of the guy who died after eating the razor blade candy) This is the first Supernatural episode she is in. She returns again briefly as Crowley at the start of season 11- when Crowley possesses Marnie, a nice Suburbs housewife and enjoys her birthday celebrations (YOLO) before getting back in touch with his minions.
Dean asks Castiel & Uriel if they are "hammers" of God. This may be both a nod to the assumption that the archangels aka Gods Army are represented as something - Castiel (Cassiel) is the Shield of God and Uriel is the Light of God, but also a reference to a well-known line from "Immigrant Song" off of Led Zeppelin's third album.