Giant Tree Frog

The Rain Frog is an anime-only animal in the 1999 series.

Appearance
The frog is roughly the same size as a Frog-In-Waiting, it has pale green skin, and big red eyes.

Behavior
During rainy weather, they are known to go berserk.

Hunter Exam arc
A tour guide to the animal show held on Whale Island, introduces the Rain Frog and details that it goes berserk when it rains and that its name is "Gaeru-chan". Later in retaliation for being locked up, Gon releases all of the caged animals at the animal show.