And then there's "The Mermaid" by (I think) Shel Silverstein - Glenn Yarbrough used to do it, had to do with "you're not gonna love the tail" - finally meets the Mermaid's sister whose "upper half was an ug-a-ly fish, but there rest of her was girl..." and ends "and I don't give a damn 'bout the upper half, if that's how I get my tail..."
Maybe not for kids, I guess.