Tympole is a round, tadpole-like Pokémon with a tan, circular face. It has large, oval, black eyes; a wide mouth with down-turned corners; and black eyebrows in the shape of quarter notes. Its spherical body is black with no visible limbs. Instead, it has two black-and-blue ringed cheeks akin to half-spheres on either side of its head. It has a long, blue tail with a fan-like shape and a black spot at its base.
Tympole vibrates its cheeks to create a sound too high-pitched for humans and other species of Pokémon to hear. The sounds are used in rhythm to communicate with others of its kind, particularly for warning of danger. They are known to sing in high-pitched voices, which creates graceful ripples on the water's surface. The anime reveals that Tympole swim and attack in groups.
Multiple Tympole debuted in Facing Fear with Eyes Wide Open!, where they attacked Oshawott underwater while under the command of a wildPalpitoad. They were trying to prevent him from getting the medicine to cure the team from the poisoning several Foongus inflicted. However, they were forced to flee when Oshawott opened his eyes while using Razor Shell.
Although it is simulated as swimming in Pokédex 3D, Tympole does not display the bubble effect that all other Pokémon simulated in an aquatic environment, such as Eelektrik and Stunfisk, display. The reason for this is unknown.
Tympole appears to be a combination of a toadtadpole and a loudspeaker. Its spherical "speakers" were probably inspired by toads' "warts" and poison glands, as well as the common Surinam toad, an aquatic amphibian whose backs are covered in pockets that hold its eggs, or more likely, the tympanum of a real-life toad, located in the same area. It is an eardrum-like body part the toad uses to hear. Its Pokédex entry also mentions the fact that it creates vibrations underwater, also like the common Surinam. Its eyebrows resemble musical notes, specifically the quarter note, and the bumps on the side of its head are similar to headphones.
Tympole may be a combination of timpani or tympani (a type of drum), or tympanic membrane (eardrum; referring to the bumps on each side of its head), and tadpole.
Otamaro may be a combination of おたまじゃくし otamajakushi (tadpole or musical notes) and まろ maro (an affectionate suffix or shaved eyebrows, the latter referring to the markings above its eyes).