Aesop's World(1999)

Aesop's World

Three kids living in the Watermill Village were planning a picnic in the mountains. Of course Pico, a young hamster kid wanted to go to the mountain peak with her friends Tocho and Fufu. The three of them fall in a hidden lake beneath the mountains and discovered a giant fish named Aesop floating. The knew that the fish wanted to fly again, in order to do that, they must collect mystical scales all across the world. Because of this, they start their search for the mystical scales in order for Aesop's dream to come true.

(Source: Anime News Network)