Frog

Frogs were amphibious creatures native to Earth. The word was also an epithet typically hurled by the British against the French.

Earth frogs
Percy Shelley in 1816 recalled how Galvani had experimented on frogs by subjecting them to electromagnetic spark, which had caused their legs to move. (AUDIO: Mary's Story)

When the Axons offered axonite to the people of Earth, they used it to make a frog grow in size, demonstrating how it could be used to solve world hunger. (TV: The Claws of Axos)

Other frogs
The Urbankans resembled frogs, as noted by the Fifth Doctor and Tegan Jovanka. On Monarch's ship, frogs were used for their poison by the Monarch. The poison had the power to shrink living people. (TV: Four to Doomsday)

Josiah W. Dogbolter was half-frog, half-man. (COMIC: The Moderator)

On an Earth-like planet, the First Doctor, John and Gillian met a race of hat-wearing talking frogs and helped them catch a shark that was trying to eat them. The frog people helped them search for the Doctor's TARDIS when it disappeared. (COMIC: Shark Bait)

On the planet Chloris, the Fourth Doctor suggested that a giant frog was responsible for laying a giant egg there. (TV: The Creature from the Pit)

One of the Eleventh Doctor's fezes was eaten by a slime-frog on the Third Moon of Puggo. (COMIC : A Wing and a Prayer)