In Bao Gong's play, Bao Gong has a crescent on his forehead. Why? There are several views on this issue: first, it is to show that he is honest and clean as an official, like a "blue sky" in the sky with a vast moon; Secondly, when Bao Gong was herding cattle in his childhood, he was kicked on the forehead by a rich horse, leaving a horseshoe print. Third, it is to show that he can go to the underworld to settle cases at night, which is obviously superstitious.
According to the research of relevant data, there was no crescent on Bao Gong's face in the past, but two white eyebrows were drawn on his black face to show the position of eyebrows and eyes. Since the middle of Ming Dynasty, Bao Gong's legend has become more and more, and some people drew a piece of white under the two eyebrows and a "Sun-Moon Taiji Diagram" on his forehead. Later, in order to make the composition beautiful, it gradually evolved into a white crescent, which mainly brought light to the lower classes.