The Invisible Giraffe
The invisible giraffe, Giraffa transparensis, probably is the most mysterious animal in the world. In fact, it is so mysterious that almost nothing is known about it. Having never been seen, the only thing we do know about the invisible giraffe is that it exists. Probably.
Ancient stories and legends from the African continent talk about an invisible animal that sometimes wrecks havoc in remote villages. It is believed that this animals is at least five meters tall (~16 feet). This conclusion was made after analyzing the wreckage of the villages it passed through (or, more precisely, is believed to have passed through). Since there is no other animal than the giraffe with that height in Africa, people have deduced that it must have been an invisible giraffe.
What does the invisible giraffe eat? Where does it live? How many of them are there? What does it look like? We don't know, and we may very well never find out.
Scientists have written entire books about the invisible giraffe, and how it might live. From the little factual evidence of its existence, they have extrapolated entire treatises, not one of which tells the same story.
Psychologists have theorized that the invisible giraffe is a safe haven for biologists that are under to much pressure to find exact results, or that have been ridiculed by their peers for mistakes made in the past. Because no matter what you say about the invisible giraffe, no one will be able to prove that you're wrong.