Frog
Frogs were amphibious creatures native to Earth.
Earth frogs
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. (DW: The Claws of Axos)
On the Urbankan ship, frogs were used for their poison by the Monarch. (DW: Four to Doomsday)
Other frogs
Josiah W. Dogbolter was half-frog, half-man. (DWM: The Moderator)
On an unnamed planet, the First Doctor, John and Gillian met a race of intelligent frogs and helped them catch a shark that was trying to eat them. The frogs helped them search for the the TARDIS when it disappeared. (TVC: Shark Bait)
References
On the planet Chloris, the Fourth Doctor suggested that a giant frog was responsible for laying a giant egg there. (DW: The Creature from the Pit)
