From wikipedia: "When the Platypus was first discovered by Europeans in 1798, a pelt and sketch were sent back to the United Kingdom by Captain John Hunter, the second Governor of New South Wales. The British scientists were at first convinced that the attributes must have been a hoax. George Shaw, who produced the first description of the animal in the Naturalist's Miscellany in 1799, stated that it was impossible not to entertain doubts as to its genuine nature, and Robert Knox believed it may have been produced by some Asian taxidermist. It was thought that somebody had sewn a duck's beak onto the body of a beaver-like animal. Shaw even took a pair of scissors to the dried skin to check for stitches."
But what if it hadn't been a hoax, but in fact some evil doctor had created a duck-beaver hybrid from spare parts?!