Why Nidorino & Nidorina evolve via Moon Stone? Clefairy, Jigglypuff and others are somewhat related to moon, night, or sleep. But I can’t find the connection with the Nido family.
Personally, I think it’s because they’re supposed to be – very loosely – based on rabbits (definitely the weirdest fµ¢£ing rabbits I’ve ever seen, though, I’ll give you that; maybe they’re influenced by jackalopes or wolpertingers or something). Rabbits are associated with the moon in China, Japan and Korea, because the shapes on the surface of the moon that we see as “The Man in the Moon” in culturally western countries are traditionally interpreted as a rabbit, often with a mortar and pestle, in east Asia. There are a bunch of different stories about exactly why the rabbit is up there and what the mortar and pestle are for, but the fact that it’s a rabbit is pretty well agreed, and this gets referenced a fair bit in Japanese pop culture (Dragon Ball had an anthropomorphic rabbit villain who wound up imprisoned on the moon; Sailor Moon’s real name, Tsukino Usagi, is a pun on tsuki no usagi, “moon rabbit”; Digimon World: Dusk gives the player a partner Digimon who is a rabbit with moon-related powers; etc). It’s a little tricky to be sure that’s the intent, but it’s the best explanation I can think of.
Aside from our brief encounter with Deoxys just outside the planet’s atmosphere in ORAS, we’ve never been to outer space in a Pokemon game. This feels strange, especially now that there have been multiple games where we spend long periods of time in alternate dimensions–space feels like a much more natural area for a Pokemon game to explore in comparison. Why do you think Pokemon hasn’t yet really explored outer space in a game?
I suspect there’s often not a good answer to questions of the form “why didn’t Pokémon/Game Freak/Nintendo do this?” A lot of the time, the truth is that the answer is just “because they did something different instead, and one choice isn’t obviously better than the other.” There’s not necessarily a logical progression that says you have to have outer space before… whatever Ultra Space is. But I think if we want a real answer… well, what would be the consequence of going into outer space, rather than using Ultra Space as a proxy to let us explore the universe? For one thing, we would in principle be able to touch back down anywhere on our home planet; there’s not really any good reason we’d have to return to the region we left from (things like Ultra Wormholes provide at least a handwavey justification for always coming back to the same part of the world you left). But I think a deeper consequence is that we see the solar system. And Game Freak is a bit weird about whether or not the Pokémon world is supposed to be Earth. After generation I, there are very few references to real places on Earth, but all the regions we’ve visited in the core series are based on real places, and the world has a single white moon that looks the same size as its sun (only I think Pokémon might believe that the moon is an independent source of light, since moonlight and sunlight are distinct sources of magical power with different effects). If we leave the planet… well, do we see Mars? Other iconic planets of the real solar system, like Saturn? Are there Pokémon on Mars? If we can visit the moon, does that force definitive answers on things that have previously been deliberately left as the subject of rumour and conspiracy theories, like the origins of the Clefairy? Do we have to answer questions about how moonlight and Pokémon with moon-related powers work? What about the gas giants? How would they even support Pokémon? Is Pluto a planet? Can the games show us Earth from space without having a clearly defined world map? Will the answers to some of these questions accidentally confirm that the Pokémon world is definitely not Earth? Granted, Ultra Space and the Distortion World raise lots of questions too, but I think for the most part they’re questions that are relatively easier to ignore. I don’t think you can let players travel the solar system without being forced to immediately take a stance on a number of things that Game Freak would probably rather leave ambiguous.