Fogg and Kady following a man wearing a brown bunny costume in the Etheric Realm satirizes the White Rabbit of Alice's Adventures in Wonderland (1972).
Professor Lipson apparently being unaware of the surname "Chatwin" when Plum reveals her full name, and making the fourth-wall excuse that she "missed an episode", is a neat in-joke upon the show's complex backstory by its final season.
Eliot quips that Seb's televisual system for publicizing his heroics is better than Netflix, but more accurately this is a magical technique known as 'scrying' - somewhat akin to a fortune-teller's crystal ball, but more like the Halliwell sisters in Charmed (1998) who would gaze into a glass bowl filled with water.
The hot dog stand is the same one which stood outside the book depository.
Fogg mispronounces the name of his favourite whisky: "Islay" is pronounced "eye-lah", not "is-lay".