And that is why you always put the seat down when you're done.
Most major cities in the world have rat problems, New York being the pinnacle of rat horror stories ever since one climbed out of a woman's toilet. National Geographic, not content with supplying terrifying still images of spiders, scorpions, snakes and other beasts for the worlds to see and fear, decided to showcase just how easily rats can crawl up sewage pipes and into your toilet to make sure you never use one in peace ever again.
On one hand we kind of admire the moxie of the rat and its Shawshank-like dedication to home infiltration. On the other, we would prefer to never have to worry about our genitals being bitten by a rodent please and thanks.