NNDN: Explanation 1

... and then all of a sudden I'm a girl! And my family's reversed too. And we're moving into the Russo's house next to the house that should be our own. "You mean I made the wish and it split me into me and you? Only you're a girl and you got the stone from your grandmother?" "That's pretty much it. Of course the stone has a range limit so I don't really have a grandmother. Nobody else remembers because only I heard the wish. Maybe you too but the way this wish worked, there's nothing for anyone here to remember anyway since in this reality I haven't met anyone in this neighborhood." "Did you try to change back? I mean, you don't have to have anyone cease to exist, you just need to be a guy." "Let me try. I wish I'm female for the next year." Then Madison realized what she had said. "What? Why did I say that? I wish I knew why...." "Don't say that!" replied Jon. "If one wish got messed up, you don't know what even a wish to know would do." "No, the wish to know worked fine," said Madison. "I wished for something interesting to happen. The 'interesting' thing can include me making further wishes. I can't believe I'm really stuck...."