Drop bears are an extremely vicious species of animal, indigenous to Australia. They are slighly smaller than the more well-known koalas, but have six-inch fangs and razor-sharp claws. Their favourite method of attack is to wait in trees over a bush path for their prey to come along, then they drop from the branches and attack their victim (hence the name, drop bears).

Their natural food is the large kangaroo, which they defeat by shredding the flesh at the base of the neck. Unfortunately for American tourists, the baseball caps that these tourists wear make them look (to the small mind of the drop bear) very much like kangaroos, and it is advised they do not go bushwalking alone, or without informing a park ranger of their intentions.

The easiest form of protection from drop bears is simply to wear an Akubra hat, which looks nothing like a kangaroo. Additionally, the drop bears have learned to avoid attacking anything wearking an Akubra, as generations of brave Akubra-wearing Australians have caused their species much damage.

Drop bear's aren't actually myths. The myth contrived to fool stupid Americans is the myth that drop bears are mythical. In 2000, I think it was, a confused drop bear dropt on the head of an old lady outside her house in a suburb of Melbourne. Fortunately, she survived, and the offending animal was (inaccurately) labelled a koala, but heed the warning, nonetheless.

Note also that drop bears tend to prefer the brain.

And also, I've heard tell of another form of drop bears that attack cars, but I can't remember what exactly they were called.