I had a random thought earlier: What if neither Cora nor Regina are natives of the Enchanted Forest?
The reason the question came up in my mind is because Cora ''became'' the Queen of Hearts entirely too easily in Wonderland. If it were that easy to earn nobility in any of the magical realms, why wouldn't she have done that in the Enchanted Forest either before or after her banishment to Wonderland? The fact that she had a thing for hearts even before that banishment suggests a lot, too.
What's more, if you take a good, long look at Regina's father, particularly his outfit, he bears a striking resemblance
to a certain inhabitant of Wonderland. Even the role he served after Regina became Queen is similar.
And then you have Regina herself. A fair, mostly innocent young woman who retained that general innocence until her mother had the love of her life murdered. If Cora was as evil and manipulative as we knew her to be, how did Regina succeed at being so relatively good for most of her life? What if, instead, she was a real girl who accidentally fell into Wonderland, thwarted Cora, and as payback Cora ''stole'' her away when they were throwing her out of Wonderland, and manipulated her into believing she was Cora's daughter?
The fact that they relied on the Mad Hatter for most of their dimensional hopping, and the Hatters obsession with Regina, is all just icing on the cake.
Like I said, just a random thought.