After defeating the ghost with the cursed mask, Charles tells Edwin that he might encounter a ghost who kills people by drilling into their heads. Showrunner Steve Yockey previously worked as a staff writer on Supernatural (2005). He wrote "Advanced Thanatology (2017)", which involved a ghost with a cursed mask who was killing people by drilling into their heads.
In the opening credits, one of the dancing skeletons does the Carlton, a dance move popularized by Carlton in The Fresh Prince of Bel-Air (1990). Then, when the team is in the malt shop, the song "It's Not Unusual" is playing very quietly in the background - the song that Carlton does the signature dance to.
When Charles & Edwin are arguing about Crystal in the closet, most of the board games on the shelf in the background are different variations of Clue.