Monk recounts singing "There are chicks just ripe for some kissin and I mean to kiss me a few". That is from the song " Lot of Livin' to Do" from the musical "Bye Bye Birdie."
[16:25] and [20:08] The book where Zacharay Ellinghouse hid the key is "Overworld: The Life and Times of a Reluctant Spy" by Larry J. Kolb.
The note that Janice Ellinghouse left herself has a misspelling of the word "mortgage" as "morgage."
When Dr Kroger makes his house call, he is dressed to suggest (to a British viewer at least) that he has been interrupted during a game of cricket. Although his shorts are a bit of an incongruity, that may be a Californian preference on show.