Wooper is a mostly blue, amphibiousPokémon that resembles an upright, armless axolotl. Wooper's head is large compared to its body, and it has small, round, black eyes. It has purple, branching gills on either side of its head; the males have more branches in its gills than the females. Wooper stands on two small, round feet, and it has a large, thick tail. On its belly are dark blue curved markings.
It is implied in the anime that Wooper is a dull-witted Pokémon oblivious to its surroundings. Wooper lives in cold water most of the time. When sleeping, it partially buries itself in the mud at the bottom. It will occasionally leave the water when the air cools in the evening to search for food along the shore. While walking on land, it coats its body with a slimy, toxic film that keeps its skin from dehydrating and insulates against the cold. The film causes a shooting pain if touched barehanded. It is a timid Pokémon and tends to stay close to Quagsire. Arbok is a natural predator of Wooper.
Wooper in the Paldea region has a brown coloration, with two pairs of bone-shaped gills branching from its head, as well as an eight-pronged pattern on its stomach. Paldean Wooper once lived in the water during ancient times until they were forced out of their territory. As a result, they gradually adapted to living on land, namely in marshes. Paldean Wooper employs two adaptations to allow it to survive on land: its gills have hardened, and it coats its body with a poisonous film that keeps it from drying out. However, these adaptations resulted in Paldean Wooper having heavy bodies and being only able to move really slowly. To defend itself, Paldean Wooper can use its gills to unleash a powerful poisonous liquid. Paldean Wooper travel and work together in groups of three or four, and enlist the help of their evolutionary relative, Clodsire, to ferry them across water. Despite the adaptational change, Paldean Wooper can still float or swim in the water.
Wooper, the Water Fish Pokémon. Though they prefer to live in cold water, these appealing Pokémon forage for food on land. They are kept warm by a layer of insulating body fluid. Wooper is the pre-evolved form of Quagsire.
Out of all the Pokéfloats, Wooper spends the most time onscreen. It first appears when the scene is on Slowpoke's tail and it then floats past Sudowoodo, Snorlax, Venusaur, and Seel before finally floating away. While its head is small, players can also stand on the gills.
Wooper appears to be based on a larval salamander, which has a flat tail and feathery, external gills. Many species of salamanders are known for their poisonous skin, which may be referenced in Wooper's Pokédex entries and Paldean Wooper's design. Wooper's Shiny sprite gives it a similar coloration to that of albino, leucistic, and flavistic color mutants, or an axolotl, a species of salamander that keeps its gills and remains in the water for all of its life because it never develops lungs.
Paldean Wooper's gills make the shape of a skull and crossbones, a hazard symbol used as a warning for poisonous substances. These bone-shaped gills, combined with Paldean Wooper's brown coloration, rib-like pattern on its chest, and the fact that it is found in a region inspired by the Iberian peninsula, together may be a direct reference to the Iberian ribbed newt. This salamander species is known for puncturing its poison-coated ribs through its skin as a defense mechanism, much like how Paldean Wooper is able to secrete poison out of its bone-shaped gills. Paldean Wooper may also be inspired by mudskippers, which are fish that are capable of living outside of water.
Alternatively, the fact that Paldean Wooper was forced out of its ancient water habitat may be a reference to the ecological issues facing the axolotl in the wild, following the destruction of the Aztec captial of Tenochtitlan and the draining of Lake Texcoco.
Wooper and Upah may be derived from wooper looper (Japanese: ウーパールーパー ūpārūpā), a marketing term created in Japan that started a pet salamander raising fad. Wooper loopers are the Japanese term for the axolotl, a species of salamander.