A duck's quack doesn't echo, and no one knows why not. The underside of a horse's hoof is called a frog. The frog peels off several times a year with new growth. San Francisco cable cars are the only mobile National Monuments. 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. 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. Blueberry Jelly Bellies were created especially for Ronald Reagan.