Little known fact #1: "Que Sera Sera" won the Oscar for Best Song in 1956. The shocking thing is that this is the only Academy Award ever won by a Hitchcock movie. He was awarded an Honorary Oscar at the end of his career, but this was the only real one.
Little known fact #2: the scene in Camden Town where Jimmy Stewart is walking down the street towards the taxidermist, and he hears omninous footsteps clattering behind him?
The row house at the end of the street behind him is where Paul Verlaine and Arthur Rimbaud lived together in 1873. That's what the trivia guides say, but re-watching the movie I recognized it instantly because also in the background you can see the edge of the Royal Veterinary College, where my wife went to school for five years--it's the more institutional-looking building behind a wall to the right of the row houses. I've retraced Jimmy Stewart's steps down that street a million times, as it is how you get to the Camden High Street.
Unclassifiable Piece of Information: There was a scene eventually cut from the movie, in which a British woman is telling Jimmy and Doris where to find somebody named Vassilly. One of the themes of the movie (Hitchcock's first after becoming an American citizen, incidentally) is the American's inability to recognize non-American accents, and so we get this bit of hilarity:
The landlady is not sentimental about Vassily. She always thought he would come to a sticky end. "Queer sex," she says darkly. "That was the trouble with him." Bob and Jill are baffled by this. But further questioning reveals that Vassily belonged to one of those queer religious sects.