The Unicorn (Shel Silverstein)

A long time ago when the earth was green, there were more kinds of animals than you've ever seen. They would run around free, while the earth was bein' born, but the loveliest of them all was the Unicorn.
Chorus: There were green aligators, and long necked geese; some humpty back camels, and some chimpanzees; some cats and rats and elephants, but sure as you're born, the loveliest of them all was the Unicorn.
But God saw some sinnin', and it gave Him a pain; and He said "stand back, I'm going to make it rain!" He said "Hey Brother Noah, I'll tell you what to do, build me a floating zoo; and take some of them green aligators, and long necked geese; some humpty back camels, and some chimpanzees; some cats and rats and elephants, but sure as you're born, don't you forget my Unicorn".
Old Noah was there to answer the call, and he finished building the ark just as the rain started to fall; and he marched in the animals two by two, and he called out as they went through: "Hey Lord, I got your green aligators, and long necked geese, some humpty back camels and some chimpanzees; some cats and rats and eliphants, but Lord I'm sure forlorn; I just can't see no Unicorns.
Old Noah looked out in the driving rain; them Unicorns were hiding, playing silly games! Kikkin and splashin' while the rain it was pourin'; oh those silly Unicorns! There were green aligators and long necked geese; some humpty back camels and some chimpanzees. Old Noah cried out "close the door, cause the rain is fallin', and we just can't wait for no Unicorns!"
The Ark started movin' and driftin with the tide, and the Unicorns looked up from the rocks, and they cried. And the water came down and sort of floated them away - and that's why you'll never see a Unicorn to this very day!
You'll see some green aligators (chorus) but sure as you're born - you're never gonna see no Unicorns.