A duck's quack doesn't echo, and no one knows why. The only 15 letter word that can be spelled without repeating a letter is uncopyrightable. Emus and kangaroos cannot walk backwards, and are on the Australian coat of arms for that reason.
Cats have over one hundred vocal sounds, while dogs only have about ten.
Camel's milk does not curdle. In every episode of Seinfeld there is a Superman somewhere. An animal epidemic is called an epizootic. Murphy's Oil Soap is the chemical most commonly used to clean elephants. The United States has never lost a war in which mules were used.