Unless you're Elvis or David Hasselhoff, the bathroom's supposed to be a place of safety where you can relax and unwind without fear. Unfortunately, as evidenced by the NatGeo clip below, the toilet you like to think of as your throne is actually a two-way door through which sewer rats can easily squirm, and potentially terrorize your dangly bits. Seriously.
Skip to 1:05 for the main attraction:
Thanks to their unique anatomical advantages -- like a collapsible ribcage and sharp claws for climbing -- rats can make short work of the pipes leading from the sewer to your porcelain commode, and the internal structure of the toilet itself is a breeze. They're also excellent swimmers, and the footage of them splashing around at the 2:20 mark is actually kinda adorable. Until you remember they're rats.
Now, while the odds of one climbing up while you're answering the call are admittedly slight, opening the toilet seat to find one treading water inside is a much more likely proposition. Indeed, the city of Seattle saw nearly 90 "toilet rat" complaints back in 2009, and while that might not sound like a lot (considering how many toilets there are), even one report seems like too many considering the futuristic age we live in.