The adorable frog-alligator-platypus tetranodon is a mix of a kappa, a water dwelling yokai, and a sumo wrestler. It even eats cucumber-like slugs (on the monster hunter twitter), much like the kappa. :
Kappa - The Kappapedia: cucumbers
Kappa, the Water Devil | Japan Avenue
Kappa yokai and Cucumber Chan" Sticker for Sale by OzzyMac | Redbubble