I think one of the best bits about Supernatural is how easily it can crossover with other programs.
Superwhoavengelock aside, it’s like…
You know the boys have an honorary Uncle Walt who’s a sheriff up in Wyoming and they have to actually behave up there because yeah he understands hunting but you better not do something illegal while you’re at it.
You know that Dean and a Raylan Givens have a bit of a rivalry/cops and robbers chase thing going between them and have since they were both quite young and green.
On eerily quiet nights, Mac Taylor keeps thinking about a cold case where three bodies were found with beautiful wings scorched onto an oak dance floor in an abandoned hotel ballroom.
Horatio Caine has been the Winchesters’ biggest adversary in law enforcement but also one of their biggest allies as well. You know he totally tangled with John and tried to help Dean and Sam in the 90’s.
Sam probably crossed paths in some way with Franklin and/or Bash when he was working towards becoming a lawyer. He probably hasn’t seen either of them since Jess’ death. He might even remember them more than they remember him.
Dean and Jane Rizzoli have some kind of past. What kind of past exactly is up for grabs. Might be sexual, might be he falls into the trap of being treated like yet another little brother who’s being an idiot.
And, so forth. Whenever you have one of those unexplained pranking episodes on a Disney program, that’s probably Gabriel messing around, etc…