When Bob Ewell is called to the stand, how does Scout describe his appearance? How does Harper Lee use a stereotype related to his appearance to suggest something about Mr.Ewell's character?

From the text:

In answer to the clerk’s booming voice, a little bantam cock of a man rose and strutted to the stand, the back of his neck reddening at the sound of his name. When he turned around to take the oath, we saw that his face was as red as his neck. We also saw no resemblance to his namesake. A shock of wispy newwashed hair stood up from his forehead; his nose was thin, pointed, and shiny; he had no chin to speak of—it seemed to be part of his crepey neck.

Mr. Ewell is described as a small man with a cocky attitude. This stereotype supports the "Napoleon" syndrome, so often referred to little men have big mouths.