There is a small industry in philosophy discussing the question, "What kind of thing is a fictional character?" One thing that I think is often not considered enough in these discussions is the large group of analogies between fictional characters and things like political borders.
If we compare "Sherlock Holmes lives in London" with "The political boundary between Texas and Mexico is the Rio Grande", there is nothing more to our use of the latter than there is for the former. That is, it's all just texts and derivatives of texts. If you go down to the border, to be sure, you'll see signs and the like indicating that the border is there, but if you go to Baker Street in London you'll see signs about Sherlock Holmes, too. One of the families of views about fictional characters is possibilism, the idea that while a character like Sherlock Holmes does not exist in the actual world, he does exist in some possible worlds. It makes a fair amount of sense of characters in stories (more than is sometimes admitted), although there have always been difficulties with the mechanics of it. If we take seriously the analogy between fictional characters and legal/political fictions like borders, it's difficult to see how it would work at all. Besides the usual objections to possibilism, all of which still apply, what would it mean to say that the political border between Canada and the United States, not existing in the actual world, exists in some possible world? Political borders do not represent physical boundaries. They just are legal boundaries, designated by legal fiction, and the fact that they often involve reference to physical features seems quite analogous to the fact that fictional characters often involve reference to them. And people do not cause wars, have riots, yell "54° 40' or Fight!" about things in merely possible worlds.
What is perhaps more generally interesting is that much discussion of fictional characters puts great emphasis on their nonexistence. Much of this discussion is vitiated by a tendency to try to smuggle ontological features into the existential operator, which is nothing more than a positing operator -- in logic or mathematics, using the existential operator tells us nothing more than that something is posited, and does not on its own give us any account of why we are positing it, which is all that could be relevant here. But the thing about political borders like the International Boundary is that they are fictional entities that do (in some sense) exist. The International Boundary, despite being entirely an artifact of the human mind, has real-world effects. (So, for that matter, does Sherlock Holmes's living on Baker Street in London, as you can see if you ever go to Baker Street in London.) When we talk about it we are not talking about a merely possible world or a semi-Platonic realm, but about the actual world as described in treaties and the like. Fictional anti-realism about political borders seems, at least at first glance, to leave us with nothing but muddled sets of muddles.
One could deny, of course, that political borders are fictional entities, but, again, there seems nothing more backing up their purported non-fictional status than we get with Sherlock Holmes. And political borders, of course, are not the only such legal artifacts that have analogies to fictional characters; they simply are an example that throw a wrench in some common assumptions about fictions.
Nothing about the analogy is determinative on its own; but it does seem that anyone seriously putting forward a theory about the status of fictional characters needs to consider it, and either extend the theory to such legal artifacts or give a principled account of why they are relevantly different.