Emerging from the Rawling's crypt, Sam and Dean introduce themselves to the groundskeeper as Mr. Harrison and Mr. Byrne. This is a reference to Talking Heads members Jerry Harrison and David Byrne.
Sam refers to a walker, saying it's like a zombie from The Walking Dead. Dean replies "I know what a walker is, Sam." Jeffrey Dean Morgan who plays their father, John Winchester, also plays Negan on The Walking Dead (2010).