Crooks as a black man in a discriminating is not allowed to share bunks with other men because he is black, so he has a room for himself far from the others, where he fixes harness. Since he is isolated, he spends most of the time in his room by himself.
Curly's wife showed how prejudice was not only only towards race, but gender as well, because in the 1930s people believed that women belonged to men and that men were superior. So they didn't even know her real name because they thought she was Curley's possession.
Curly's wife is promiscuous. Although she and Curley have just gotten married, she is looking for an affair. Gossip tells that someone at the ranch is the person she is having an affair with. This shows how she is unfaithful and dishonest to her husband.