The room that Harrison was told to clean is 237 which is a reference to the movie The Shining.
The hospital Dexter Morgan is admitted to, is the same location as the jail Frank Castle was detained at in The Punisher season 2 episode 3.
Marc Menchaca plays a ride-share serial killer known as 'Red'-a.k.a. 'The Dark Passenger'. Interestingly, his character in Ozark, Russ Langmore, also shares the nickname 'Red,' creating a subtle throughline in Menchaca's portrayal of intense and morally complex roles.
Dexter uses the alias 'Dr. Patrick Bateman' to procure M99 (Etorphine) from a veterinarian. The name is a sly nod to American Psycho, where Patrick Bateman (played by Christian Bale) is a Wall Street executive who conceals his psychopathic alter ego and serial killer instincts behind a polished public persona.
The address 'Hunter's Ridge,' used by the veterinarian who ships M99 to Dexter (you can clearly see this address as Dexter opens this order), serves as a clever Easter egg. The name evokes imagery of hunting-subtly reinforcing Dexter's identity as a predator who stalks his prey under the guise of normalcy.