We know what you're thinking: No one is allowed to bite your tongue but you. Well, fear not. You're probably safe, unless you happen to be a rose snapper. If so, we recommend steering clear of the Cymothoa exigua isopod. These little crustaceans, which suck the blood from the gouged tongues of fish after entering through their gills, will go one step further with you: They will actually replace your tongue and live off your blood supply — all while making little C. exigua babies in your mouth [source: Simon].
Isopods are a widely varied group of crustaceans, most of which live in the sea and many of which could easily have made the look-like-a-monster parade [source: King]. But these buggers compare unfavorably to the love child of an albino wood louse and that mind-control bug that crawled out of Chekov's ear in "Star Trek II: The Wrath of Khan." Besides, this lingua-licking louse is the only known animal parasite that functionally supplants a host's organ, which we think earns it a mention on principle alone [source: Simon].
So next time you catch a rose snapper, pay close attention when you reach past those staring eyes and open the mouth. You might be in for a monstrous game of peekaboo.