We are told that the Soul Eater was buried by the Chumash, a real life Native American tribe who also featured in Pangs (1999).
The title "Calvary" references the site outside of Jerusalem where Jesus Christ was allegedly crucified. Another name for the place Calvary is Golgotha, which means the place of a skull. Among other possible reasons for the writers to choose this title, Charles Gunn and Connor have to go to a site where a Soul Eater has been buried, chop off its head, and prepare its skull for a re-ensouling ritual - hence making that scene a Golgotha, a place of a skull.
Angelus echoes Faith's words when she is posing as Buffy in Who Are You? (2000) when he says "being evil is wrong."
Angelus reveals that Angel had suspected that Fred and Gunn killed Professor Oliver Seidel in Supersymmetry (2002), despite apparently accepting their story that Seidel fell into his own portal. He had been uncertain whether it was Fred or Gunn who actually killed him until now.
Lilah's connections and ability to procure extra-dimensional materials-even when destitute and living in a sewer-explains why Jasmine had the Beast wipe out all Wolfram & Hart employees, not just Mesektet or the Los Angeles branch. Their resourcefulness was too much to risk, and indeed just the knowledge that something had wiped out all traces of the Beast in the entire dimension did alert them that they were dealing with something far more powerful than they had heretofore imagined.