We don't often talk about the production design of the show (and more's the pity because quite often it's absolutely wonderful), but I have to say that I've always loved how the show illustrated Julia's journey to 1897 as not just passing through the door with the hexagram on it but as passing through a series of doors:
Fill in the blank: 'Charity' - "I'm scared to my wits' end! If that strange woman can just show up outside the door, what's to prevent ________ from showing up too?!"
Fill in the blank: Edward - "Miss Trask, you will find that I'm completely immune to your wiles!" 'Charity' - "Oh, ducks, no man is immune when ol' Pansy ________!!"