Cetoddle is a white round cetacean Pokémon with large eyes, a large curved mouth, long fin-like forelimbs, a large tail, and two stubby legs. There are pink accents around its eyes, on its hands, below its feet, and on its tail; and it has a single horn on its forehead. When Cetoddle opens its mouth, a single rounded tooth can be seen on its lower jaw.
Cetoddle is thought to be a close relative of Wailmer. However, unlike Wailmer, who once lived on land before becoming a sea-dwelling species, Cetoddle used to live in the ocean a long time ago, before it migrated onto land. Cetoddle live in cold regions, in pods consisting of around five individuals. It loves minerals found in snow and ice.
Cetoddle and its evolved form, Cetitan, are the only known Pokémon capable of learning the move Ice Spinner by leveling up.
Cetoddle appears to be based on various Arctic cetaceans. Its general appearance and shape may be based on the bowhead whale (also known as the polar whale or the icewhale), its white coloration and large head may be inspired by the beluga, and its singular horn may draw inspiration from the narwhal. It also appears to be based on toddlers.
Cetoddle's history of migrating from the ocean and adapting to living on land is an inverse of how cetaceans evolved in real life, as they started out as land animals that migrated into and adapted in the water. Cetoddle may also draw inspiration from the ニンゲン ningen, which are bipedal, whale-like cryptids of modern Japanese folklore.
Cetoddle may be a combination of cetacean or Cetus (a sea monster in Greek mythology whose name became the etymology for the word cetacean) and toddle (to walk unsteadily) or toddler.
Arukujira may be a combination of 歩く aruku (to walk) and 鯨 kujira (whale).