This is a submission for the Anatomically Correct Series
Kappa are creatures from Japan said to lurk in rivers and lakes. They are described as small humanoids resembling a cross between a monkey, a frog, and a turtle with either a water filled depression or a patch of water soaked flesh atop its head (which is supposedly the source of its strength) surrounded by a ring of hair. It’s said to have a penchant for drowning people and eating their intestines, has a fondness for cucumbers and sumo wrestling, and the ability to fire off high powered farts at will. The question is whether they could evolve in nature.