The Fiji Mermaid
But enough of our pseudo-sideshows; let's get to the real thing! And by the real thing, we actually mean the totally fake thing that was discovered to be an utter hoax. A selection of bizarre sideshows wouldn't be complete without a few made-up "wonders," and one of the most well-known swindles was the Fiji (sometimes called Feejee) mermaid.
It all started with a Dr. J. Griffin who came to New York in 1842, supposedly in possession of a mermaid caught off the coast of the Fiji Islands. The press got wind of the mermaid, and Dr. Griffin whetted their appetites with a peek. However, P.T. Barnum explained to the newspapers in town that the doc wouldn't give him permission to display the creature — but maybe they'd like the woodcut of the beautiful mermaid that he now couldn't use on his own publicity? They sure would, and soon the public — enticed by the image printed in all the papers — demanded an in-person look at the creature.
Guess what? It was a big hit, despite the fact that Barnum had set up the whole thing. Griffin was a guy name Levi Lyman, the backstory was fake and the mermaid was (most likely) a monkey head stitched to a fish's body [source: Hoaxes.org].