The interior of Matthew Teeger's house is a redress of the set for Ambrose's house used in Mr. Monk and the Three Pies (2004) and Mr. Monk Goes Home Again (2005).
Randy brings up (albeit tangentially) The Terminator (1984), relating to the theory of a killer murdering girls with the same name, which is what that film's title character does to a series of women named Sarah Connor in search of the mother of John Connor.
When Monk is talking to Dr. Kroger (after having disturbed the doctor and his wife by phone call in the middle of the night following a "Psycho"-like encounter with a taxidermied body), he asks if Dr. Kroger's wife suffers from Tourette's Syndrome. After a momentary pause to figure out why Monk asked him that, the doctor unconvincingly says yes. People with Tourette's sometimes have uncontrollable urges to spout profanities.
Lt. Randy Disher is disguised as Matthew Teeger's mother, Julie. In the surveillance van, one of the detectives says "we hit a new low." Captain Stottlemeyer replies, "Actually we haven't," likely referring to Mr. Monk and the Missing Granny (2004)(#2.13), in which Disher went undercover dressed as a homeless bag lady.
Actor John Hawkes plays Matthew Teeger, a sort of non-lethal version of Norman Bates (Psycho (1960)). Coincidentally, Norman Bates was played by Anthony Perkins and Teeger by Hawkes, whose real name is John Marvin Perkins.