The Leopard Seal is the secondary antagonist from The Pebble and the Penguin.
The leopard seal first appears after Drake throws Hubie into the water. In the water, the leopard seal appears and tries to eat Hubie. Hubie narrowly escapes the leopard seal and climbs on to a piece of ice where he is swept away from Antarctica.
It is later seen again when Hubie an Rocko jump into a fishing hole and swim deep down under the ice. They encounter the large seal and accidentally wake it up from its sleep. It slowly follows the two until they notice it then the leopard seal swiftly chases Hubie and Rocko up to the surface.
The leopard seal makes one final appearance jumps on the large submarine. It gets kicked in the nose by Rocko and gets kicked again in the nose even harder from Hubie which causes the leopard seal to fall into the water and is never seen again.