How is Curley characterized, and why does he react to George and Lennie the way he does?

Curley is characterized as a little guy, who wants nothing more than to prove himself. Big men, particularly big men like Lennie, seem to be a threat to his manhood, thus, he quickly uses his position at the ranch.... in addition to his fists, to prove he's just as strong and tough as anyone else. This is often referred to as the "Napoleon complex".