Okay, random idea...
A story where humans are really weird for liking other alien species. Not like in a cross-species romance sort of thing (though that too), it’s just that we legitimately find every other race in the universe cute and they have no idea how to deal with it. Like, some aliens are coming in for a delegation, and they are scaley motherf***ers with claws, teeth and everything, and they start to apologize for their appearance (because most other species they encounter are freaked out by them) and then one of the human interns starts squealing because there’s a baby dinosaur hiding behind his mommy (because mommy’s scarier so he feels safer).
Like, we as a species have an incredible fascination with other species’s children and how cute they are. Like these people understand wanting to eat smaller things because they look tasty but they have never encountered nutjobs who want to cradle the little guys with hedgehog spines on them. They have no frame of reference for our obsession with alien children.
They’re like “uh, are you alright?” “Oh my gosh they’re so cute!!!” “I was…unaware that humans had external eggs…” “oh, we don’t, but oh my gosh they’re so cute I can feel their little legs kicking!” “Okay…”
And of course, once earth realizes that some other species have overpopulation problems, almost immediately someone proposes an interspecies adoption program which is approved with near unanimous approval by Earth-gov which kind of freaks out everyone else because literally nobody had even considered it (and despite the fact that humans are one of the most colonization obsessive peoples because they have their own overpopulation problems). Not because they opposed it morally, but because some of these guys breath pure nitrogen, and others exude cyanide from their pores so they don’t think we’ll handle it well. But they figure, why not, and they start it, but earthlings are the only ones who actually receive children because everyone else is a little too wary of adult earthlings to deal with their offspring.
That’s how earth becomes just inundated with tons of species of aliens and every visitor to earth is just astounded by the diversity. Like, a human couple is just walking around with a 6'2 Karalaxian named Bob who they keep refusing to get ice cream because he misbehaved in the store.