Jackie Earle Haley is actually an accomplished drummer, and performs all his own drumming in the episode.
When The Terror is 1st shown playing the drums, Bill is shouting at him he's dragging and other obscenities. This is a reference to the movie "Whiplash" staring J.K. Simmons and Miles Teller.
Overkill's outfit in the graveyard scene is similar to Arnold Schwarzenegger's "Terminator".