An odd looking berry for sure, frog berries are a cold season berries found exclusily in December. Frog berries have a jelly texture but a very sweet and fruity taste, they make a greay candy replacement and are packed with vitamins. The darker circle in the middle is the berries seed, its see through which makes it look like frog spawn almost... 

Using frog berries gives your character jelly body parts/ innards.