A frog was a tailless amphibian found on several planets, including Earth. A toad was a type of frog adapted to dry environments.
The ancient Greek play The Frogs included an interlude featuring the croaking sound of frogs. (TOS: "Plato's Stepchildren")
Kirayoshi O'Brien owned a stuffed toy frog named Mr. Froggy in 2374. (DS9: "Time's Orphan")
During anomaly consolidation duty on the USS Cerritos in 2381, Ensign D'Vana Tendi found the skull of a large frog from a planet "where everything evolved all weird" in Commander Jack Ransom's office. The skull began to glow and shake when Ensign Sam Rutherford picked up its sample container with tongs, causing him to drop and break both the skull and its container. The broken skull then exuded a vapor that triggered full molecular engorgement in Rutherford after he inhaled it. (LD: "The Spy Humongous")