One idea that’s shown up several times in Oz and related books is that of a place where everything is double. I believe the first appearance of the theme is in The Enchanted Island of Yew, in which Prince Marvel and Nerle visit the hidden Land of Twi, located in the middle of a thick hedge near the Kingdom of Spor. L. Frank Baum describes this country as follows: “Before them were two trees, exactly alike. And underneath the trees two cows were grazing–each a perfect likeness of the other. At their left were two cottages, with every door and window and chimney the exact counterpart of another. Before these houses two little boys were playing, evidently twins, for they not only looked alike and dressed alike, but every motion one made was also made by the other at the same time and in precisely the same way. When one laughed the other laughed, and when one stubbed his toe and fell down, the other did likewise, and then they both sat up and cried lustily at the same time.” Mind you, this could potentially lead to a bit of a paradox. Baum mentions “the double doors of the double houses,” but if both the houses AND doors are doubled, then wouldn’t that mean FOUR identical doors? Where does the doubling end? There is no word “one” in the language of Twi, although they do use the term “singular.” Twi exists in perpetual twilight, and is ruled by women called the High Ki, assisted by the Ki and the Ki-Ki.
When it looks like the High Ki are going to order Marvel and Nerle to be executed, the fairy prince splits the double leader into two separate individuals. This leads to civil war, but Marvel manages to stave off serious trouble by calling in his allies, King Terribus of Spor and the reformed bandit chief Wul-Takim. The prince then restores the High Ki, and they and the Ki accompany him on his journey. They later return to Twi and have the hedge restored, which might mean that the isolated land remained as it was when the rest of the Isle of Yew became civilized.
Ruth Plumly Thompson also uses the double idea with Double Up, a city in the Winkie Country introduced in The Purple Prince of Oz. In this place, “the houses were double, the windows and doors in the houses were double, the double-faced citizens walked stiffly in pairs.” The residents each have two faces, one on each side of their heads, like Janus or the Scoodlers. These faces frequently talk at once and contradict each other. The ruler is known as Too Too the Second, King, King, and Double King.
Double Up is one of Thompson’s typical hostile communities, where the army disguises themselves as a marching band and then knocks out strangers with sliding horns. The Doubles capture Randy, Kabumpo, and Jinnicky, locking the boy in the dungeon and trapping the elephant in a log enclosure. The Jinn uses his blue incense to put the Doubles to sleep, allowing his party to escape. And in Sissajig, Two City is a place where the people generally do everything in pairs, wear two hats each, and have doors with two knockers and gardens with two gates. The rulers, the Duchess Guess Sue and the Duke Me Too, apparently do not have twins, but they do each wear two crowns. The Duchess also has a double chin and wears her hair in a double pompadour.
Finally, there’s Twinlet-Town in Frank Joslyn Baum’s Laughing Dragon, part of the area of the Quadling Country ruled by Princess Cozytoes. It’s inhabited by sentient flowers that are all double, and think single people are incomplete.
Unlike the inhabitants of the other double communities, however, the flowers are friendly to strangers. The town is famous for its double pools made of children’s tears, and it is governed by the Perfumed Council.
There’s a guest room in the double castle that’s made to accommodate humans, particularly the Princess when she visits.