This episode was part of NBC's 75th Anniversary celebration, in which actors from previous NBC shows guest starred in current ones.
Jack Klugman, who plays the retired medical examiner, created the role of "crime solving coroner" (now popularized in Bones, Rosewood &, of course, Crossing Jordan) in Quincy M.E. back in the 70s.
The mortician creeping around the crypt who hits on Lily says he's from Fisher and Sons. That is the same funeral home on HBO's Six Feet Under.