If you look carefully at the dark shadows on the full moon, you may be able to see Wu Kang chopping down a cassia tree.

In Chinese mythology, Wu Kang is portrayed as a woodcutter fascinated with the magic of immortality. Angered by his hubris, the gods banished Wu Kang to the Moon Palace telling him that he must cut down a huge cassia tree before he could return to earth. Though he chopped day and night, the magical tree restored itself with each blow, and thus he continues to eternally chop the cassia on the barren moon.