Yesterday's story references a bit of personal canon about the Giles family: that Lionel Giles, who did an early translation of the The Art of War, was Rupert Giles's great-grandfather. One may further speculate about Slayers, their Watchers, and the actions of certain vampires during the Boxer Rebellion.
Tell me about similar bits of personal canon you have, where real history fits in neatly with fiction.
Random: Garfield without Garfield. Pure genius.