One evening Ganesha had eaten a great many sweet modaks. As he rode home on his little mouse, the mouse stumbled, and round Ganesha rolled gently onto the ground.
The moon, watching from above, burst out laughing at the sight. Ganesha did not like being mocked, and he declared that the moon would lose its light.
The moon was very sorry. So Ganesha softened the lesson: the moon would fade and return, growing and shrinking through the month — a gentle reminder not to laugh unkindly at others.