Kappa are legendary creatures from the Japanese folklore. Kappa live in rivers and have a kind of human body with a strange bird/tortoise face. They behave quite like humans and can even speak. Kappas are rather nasty creatures which can even eat children. These legends frighten children and prevent them from playing too close to rivers.
In Tokyo, close to the area of Asakusa, a road called kappabashi (bridge of kappa) is decorated with pictures of the kappa. A local small temple is devoted to the kappa and offerings of cucumbers are made as it's a vegetable kappas seem to like. In the temple you can see what is presented as a mummified hand of a kappa.