Oshawott is a bipedal sea otter-like Pokémon. It has a spherical white head with small, triangular dark-blue ears on the sides. Oshawott's eyes are dark and its dark-orange nose is shaped like a horizontal oval. Several freckles cover its cheeks which may be premature whiskers, and two pointed teeth can be seen when it opens its mouth. The light blue fur on its body forms bubble shapes around its neck. Its arms are white and rounded, while its feet are dark blue with three toes each. It also possesses a rudder-like dark blue tail. It carries a pale yellow seashell called a "scalchop" on its belly. This shell is made of the same material as its claws, and is used for both battle and cracking hard berries. If heavily damaged or lost, Oshawott can grow new ones from its body, though it can take weeks. 
Oshawott, along with Tepig and Snivy, appear when Black accidentally drops his box containing the Pokémon. When Tep and Snivy begin fighting, Oshawott attempts to break them up, only to get hurt in the process. After getting annoyed, he attacks them and sends Tep running off. He was later chosen by Bianca because she thought he was cute. He first appeared in Fussing and Fighting.
Oshawott appears as a Poké Ball summon. It behaves similarly to Piplup in Brawl.
Oshawott trophy in Super Smash Bros. for 3DS
Oshawott also appears as a trophy in both versions of the game.
NA: Oshawott carries a little weapon on its stomach known as a scalchop, which can be used to either defend or attack. Its Surf move can knock opponents off the stage, but if you use a reflecting move at just the right moment, you can turn the tide against it!
PAL: Oshawott carries a little shell on its stomach known as a scalchop, which can either be used as a weapon or to defend against attacks. Its Surf move can knock you right off the stage, but if you reflect it just at the right moment, that could really turn the tide back in your favour.
Oshawott appears as one of the player character in PokéPark 2: Wonders Beyond. He's a self-proclaimed investigator for the Cove Area. At first, he is suspicious of Pikachu and attempts to interrogate him, until Piplup tells Oshawott that Pikachu is a friend. Oshawott later chases after Pikachu and Piplup after they enter the Wish Park, and narrowly escapes from Cofagrigus with Pikachu. Oshawott's boss and mentor, Samurott then orders Oshawott to work together with Pikachu to investigate the Wish Park and anyone involved, and to rescue Piplup.
Oshawott has the lowest base stat total of all Water-type starter Pokémon.
Oshawott is the only Water-type starter Pokémon that is not a member of the Water 1 Egg Group.
Oshawott was designed by Yūsuke Ōmura. It was also the last Generation V starter Pokémon to be created, with the staff noting that they always have some difficulty coming up with concepts for the Water-type starters.
In Pokémon Black and White, Oshawott, along with Snivy and Tepig, has the lowest experience yield of all Pokémon, with a base value of 28. This was done specifically for the first two battles of the games, so the player's starter wouldn't level up after defeating Bianca and thus have a level advantage over Cheren.
Oshawott is based on a sea otter pup and samurai. Sea otters are known for using tools, including clam shells, with their forelimbs; the placement of Oshawott's scalchop is reminiscent of the way a sea otter looks when cracking open its prey against the tool on its stomach. This scalchop also holds similarities with Japanese war fans, which were often used by samurai for defensive purposes. Ken Sugimori said that Oshawott and its evolved forms were the hardest for the team to design during production, as conceptualizing its evolved forms were difficult. They eventually settled on a samurai theme, and a trip to an aquarium inspired them to incorporate elements of sea lions.
Oshawott may be a combination of ocean, shell, water, wash, and otter.
Mijumaru may be a combination of 水 mizu (water) or 未熟 mijuku (naive or immature) and 丸 maru (round). Maru is also a common suffix in male Japanese names. Miju may also refer to an otter named Mijbil, the subject of an autobiographical novel and movie called Ring of Bright Water.