Penguin, Reindeer and Fox were great friends. One day, Penguin and Reindeer found a load of fruit, and decided to keep it a secret. On the way, they met Fox, who seeing them so happy, asked them why. They told him they couldn't say, because it was a secret, but Fox asked them to trust him, so they told him about the fruit.
When they arrived at the village, Fox forgot about his promise, and told everyone. When Penguin and Reindeer returned to the place where they had found the fruit, the animals of the village had already been there and eaten it all.
That same day, Penguin and Reindeer found another place full of food, and the same thing happened again with Fox. Angered by these betrayals, they decided to teach Fox a lesson. The next day they told Fox that they had found a lake so full of fish that no effort was needed to catch them. Fox again told everyone in the village about this. The next day, Fox came by, covered in cuts and bruises. After telling all the animals about the lake full of fish, everyone, including even the polar bears, had gone there. But, not finding anything, they felt deceived, and had given Fox a good beating.
Fox learned that keeping people's trust is very important, and that to get it in the first place you have to earn it with loyalty and always keeping your word.
Penguin and Reindeer devised another trick for Fox but, as he was no longer a bigmouth, he did not betray them, and Penguin and Reindeer regained their faith in Fox, thus forgiving him.