Defictionalization: My terrific taste for metafiction aside, this also happens in-world, quite a bit.  Most notable, perhaps, is the incident (see: Stranger Than Fiction) in which the protagonist species from the virtuality game (novel, InVid, watchvid, and slinky) An Ending Not In Fire, the temísi, arthál, and zal!en were created as real, self-perpetuating species, given homeworlds, and thus acquired existence, but that’s just the far end of a long curve.  Meris Vinithos-ith-Vinithinios went farther than most, but the galaxy’s full of very wealthy people with plenty of money and time to spend on making their fantasies real, and no particular reason not to.