Bubbles
Bubbles is a Unique Leviathan with his own art who comes with Anna when you rescue her. Unfortunately despite his unique artwork, he does not get his own gallery entry.
Bubbles doesn't seem to be a normal Leviathan, as he lack the usual traits inherent to them: Pack Mule, WaterMount, and Aquatic. Bubbles is also slightly unique among Creatures in that he can come with maxed morale instead of being locked at 50 like all others, though he does not benefit from this in any way. He's just a happy fish.
Bubbles normally doesn't gain any ap unless engaged. Anna has a unique skill, Command, which gives Bubbles 2 ap. Naturally this skill is crucial to utilize this powerful, unique pet. Additionally, the Command skill is inheritable, so you could create an entire team that can make Bubbles an enemy wiping machine.