Cleffa

Like Pikachu, Clefairy was given a pre-evolution in the second generation of games, coinciding with the introduction of actual pokemon breeding mechanics. They sort of went hog-wild with these for the Gold and Silver games, but subsequent generations have introduced "baby" pokemon more sparingly or not at all. I could go either way on this, personally. There are pokemon who could still use a "prevo" as we took to calling them just because it doesn't make one damn lick of sense how something like a Lapras hatches straight out of an egg, but on the other hand, this is pokemon we're talking about. Why waste a slot for an entire new monster just to rectify a logical gap? I'm glad they don't toss around "babies" so much these days.

Anyway, it's also interesting that the Clefairy line is repeatedly said to come from the moon, or have arrived on our planet from a meteor. Of course, if you ask me, all pokemon are pretty obviously from space. I even got paid real money once to posit my pokemon theories. The internet is magical.