Above, a "Shredder" Clam (Antiprismadus triskaidecadontus) opens up to allow its teeth to be cleaned by a "Nagonna" Bird (Pluvianus nonagontus). This behavior is not uncommon in nature.

Below, a few of the 320 extant forms of P. nonagontus.

Below, some specimens of Cupolazoa, a type of multicellular creature found in standing urban waters. In spite of lacking flagella or opposable thumbs, they appear to engage in underwater racket games and other recreations.

They are not often observed, due to their propensity to fold up into a protective shell-like structure when disturbed.