Frog

Frogs and toads (note that a toad is a type of frog) have appeared in several Castlevania games.

The first time a frog-like enemy made an appearance in Dracula's Castle was the Tadpole boss in the Konami mascot game Konami Wai Wai World, which featured levels of several different Konami franchises. This enemy appeared as a giant frog with one eye and hopped about the place and attacked with its massive tongue. This was the only boss in the Castlevania stage that you had to defeat (you could skip past Dracula). It guarded the key that you needed rescue Simon Belmont. This is also the only time where a frog-like enemy was a boss.

The next appearance was in the Japanese version of Castlevania III: Dracula's Curse, where a Frog is used instead of the Hunchback and acts as a common Hopper. Frogs later appeared as unique enemies in their own right in Castlevania: Rondo of Blood and gained the ability to strike with their long tongue.

An endless supply of larger Toads sprung from the swamp areas of that game and hopped about. These were present in all regions of the game. This kind of toad reappeared in the swamps of Super Castlevania IV and Castlevania Chronicles.

In Castlevania: Symphony of the Night, both frogs (the first time normal frogs were seen outside of Japan) and toads have the ability to attack with their tongues. After a relatively long absence, Frogs and Toads made a return in Castlevania: Portrait of Ruin, where Charlotte Aulin gained the ability to turn herself or Jonathan Morris into a frog in Castlevania: Portrait of Ruin, gaining access to hard to reach areas. They have not appeared in a 3D game to date.