The moment when Dean, dressed as a priest, grabs a cocktail sausage and eats it was improvised by Jensen Ackles on the day. The sausages were technically edible but had only been intended to be there as props, and Jensen recalls that they didn't taste good at all. But the action led to the writers scripting similar stuff, which helped develop a defining characteristic of Dean Winchester's: his love for snacks and fast food and his penchant to eat practically anything in front of him.
Sam and Dean introduce themselves as Father Simmons and Father Frehley, the bassist and former lead guitarist of the rock band KISS.
Director Philip Sgriccia personally chose to use two early Bob Seger songs because he was from Michigan, and "Nightmare" took place in Saginaw. In addition to this, Sgriccia asked his sister to send him coffee mugs and baseball caps from Michigan to give believability to the setting.
Dean says "He's a spoon bender" in reference to telekinesis, is actually a reference to Uri Geller, a famous telekinetic artist from the 70s and 80s.
Actress Beth Broderick is most famous for her role of Zelda Spellman, one of two Sabrina's unconventional witchy aunts, on a popular TV series Sabrina the Teenage Witch (1996) starring Melissa Joan Hart as Sabrina.