World Builds Itself

''That wasn't there before. Neither was that. Or that. Or that. Or... (sigh)''

If it looks like there are more plot elements that are being added to the story that have never been there before or even mentioned, that's because The Word Builds Itself. This is when large, major parts of the planet seemingly come into being out of nowhere for the convenience of the story being able to continue.

This UnTrash is commonly due to bad writing not planning the future of its franchise out well or at all. It isn't limited to just areas of the world appearing out of nothingness; it also includes people and objects that are included to the plot with little to no explanation of how they got here or even a bad in-universe reason to why they suddenly showed up despite not being at least alluded to in the past.

Franchises where The World Builds Itself
Pokémon - Ever since gen I, the world of Pokémon seems to be expanding itself and having locations in it that should've been noted even as far back as the days of Red, Blue, Green, and so on. For some strange reason, nobody in earlier generations knew about major details of the Pokémon world even when the in-universe logic says they should have since these details existed even in earlier generations.

South Park - South Park. The little mountain town that keeps growing in more sense than one. Over the course of the show, South Park slowly started to grow from a little mountain town to more of a below-average city with more people and buildings seemingly just spawning into existence without warning.