The Waddlepus is a member of the Unknown Family in Pikmin 3. It is an Octopus-like creature that is mainly here to bother the captains rather than killing Pikmin.
The Waddlepus is sleeping most of the time until it spot a potential threat, it will then inflate its head and start walking toward the group. When it is at a good distance, it will blow bubbles that will project the Pikmin and captains traped inside away from the Waddlepus. If the captains throw Pikmin on its inflated head, the head will also generate bubbles to make them go away.