I found a new nice story of Guan-Yin:
Story of Guan-yin The Goddess Of Mercy-佛門網 ：開啟佛教大門 ...
[www.absolutechinatours.com/...of-Guanyin-in-China.html - Cached]
One famous story about the show-up of Guanyin（观音现身）dates back to Tang
Dynasty during the reign of Emperor Wenzong(唐文宗, 827~840A.D.). It is
known that the capital of Tang Dynasty is Chang’an(Xi’an nowadays), a
great city in the west of China, a city that turns its face to the
empires of Inner Asia. Emperor Wenzong has a special hobby of eating
clams, ordered clams for three of his five meals, each and every day.
However, based on the geographic position of Xian, it was a great
barrier to bring clams from the sea to the imperial palace. Such a
delicacy the emperor ate was through the bitter labors of thousands.
To ensure the freshness of the clams, every day in the dim light
before dawn, clams would be gathered by the ocean fishermen of
Zhejiang and then packed by porters in cold seaweed, wet sand and ice,
then rapidly loaded on relay mounts that sped the Imperial highway.
Obviously, it is a great sacrifice of the labors only to please the
emperor’s eating preference.
Day after day, the laborers suffered a lot from the process of hard
work; many of them are living in misery, until one incident shocked
the entire palace. One day, the Royal chef discovered an unusual clam
in grand size. The clam was enormous-twenty times the usual shell,-
surely an imperial clam meant for the Imperial Palate. As the Clam
Shell Opener stepped up to pry the shell apart, however, he found the
shell sealed like iron; the clam was as tight as a rock crevice on the
slope of Mount Tai.
Emperor Wenzong heard about this and commanded the opener to let him
take a closer look. All of a sudden, as if by signal, the clam began
to open automatically. The emperor gasped at what he saw. There,
standing inside, was a finely detailed, miniature, astonishingly sweet
statue of the Goddess of Mercy, the Bodhisattva Guanyin, exquisitely
carved. What surprised him most is what Guanyin said by her lovely
expression, “The laborers have to make great efforts for your own
pleasure; both harass the people and waste money”. Then the Emperor
realized that Guanyin –the Buddhist Goddess-who hears even the
smallest call for mercy from even the tiniest voice in the empire-had
taken pity on the boat men, the fisher folk, the portage men and relay
riders, even the royal cooks-all who served his royal taste and royal
whim. He realized that the purpose that Guanyin show up in the grand
clam is to warn him; she would watch over mankind in times of fear and
danger. (Partly Refer to "In the Realm of the Gods: Lands, Myths, and
Legends of China").