In the pilot episode, Jessica wears a Smurfs t-shirt.

Ridge Canipe, Dylan Everett, and Nicolai Guistra have all played Young Dean Winchester in various episodes. Colin Ford played Young Sam.

When Dean is sent to Hell at the end of the third season, it is the demon Alastair who tortures him, stopping only when he finally convinces Dean to torture other souls himself.

In "I Believe the Children Are Our Future", a young boy with strange demonic powers turns Castiel into an action figure.

The men of letters are identified with the crest of the Aquarian Star, a six-pointed sign (or unicursal hexagram) that represents great magic and power and was linked to the gates of Atlantis.

Gavin MacLeod was the Scottish son of Crowley, when he was a human named Fergus Roderick McLeod.

In the pilot episode, Dean gives his name as "Ted Nugent" when he is being interrogated by the police.

The Men of Letters Bunker, or "the Batcave" as Dean calls it, was the secret base of operations for the Men of Letters.

After killing the Wicked Witch with the Ruby slippers and closing to door to Oz just in time to stop the Flying Monkeys from reaching earth, Charlie Bradbury joined Dorothy in her quest to rid Oz of the witch's evil forces for good.

In "Beyond the Mat" (Season 11, episode 15), Dean meets one of his childhood heroes, the wrestler Gunner Lawless, and informs him that he got his first "B&E" for breaking into a house to watch Lawless' cage match on the homeowners' pay-per-view.