Upon closer inspection, I realized that it was the toy-maker's rendition of an honest-to-goodness, real-life creature from Mother Nature's menagerie. It was a plaything that depicted an axolotl.

Now, it seems, they’re everywhere: in the form of plush toys, children’s books, fashion and decor. But the axolotl is only the latest creature to charm kids and mystify their millennial and ...