archive footage used for flashbacks
Castle carves a pumpkin to look like Max Schreck from this movie.
Alexis names her fake egg "Fagin".
When Alexis is asking for permission to go to the senior party, Castle says, "Father won't be quite himself" and laughs maniacally, referencing Norman Bates' comment about his mother.
Seamus Dever character is dressed with a Doctor costume reminiscent of the one he used as Dr. Ian Devlin in General Hospital.
Castle tells his daughter, "I have taught you well, Grasshopper."
Castle mentions Dr. Frank did Brad Pitt's veneers
Castle references Buffy while standing over a body in a graveyard, with a stake in the heart.
Castle's Halloween costume is a "space cowboy." Nathan Fillion is actually wearing the exact outfit he wore as Captain Mal Reynolds in "Firefly" (2002), prompting Alexis to tell him to retire it; in-joke as Nathan Fillion is spoofing himself
Castle mentions the war between vampires and Lycans.
Alexis tells him to retire it "because he wore it like five years ago." This episode is about five years after the Firefly feature-film, Serenity.
Detective Espisito attends Castle's halloween party dressed as a soldier, mirroring Jon Huertas' role in Generation Kill as Antonio 'Poke' Espera
Kate and Castle talk about Frank Miller's artwork. Stana Katic played Morgenstern in this movie, written and directed by Miller.