Most of Steinbeck's characters in Of Mice and Men represent stereotypes, not just from his time period and the migrant worker arena, but from life in general.
Carlson--He is a big bully. While Curley is also a bully, he picks on others because he is insecure about his short stature. Carlson is simply cruel and likes to use his prized possession--his Luger--whenever he gets an opportunity to do so. He lives during a time when few men had personal possessions of any value; so he represents how those possessions gave people power and a sense of pride during such harsh times.
Candy and his dog--Candy is an old ranchhand who was injured on the job. He has lost his hand and only able to do handyman work around the ranch. Steinbeck uses Candy to illustrate what happens to a man when he feels useless. Candy and his dog roam the outskirts of the worker societal structure; they're merely spectators. Candy's dog is killed simply because he's old, and Candy wishes that someone would put him out of his misery when he's "useless."
Slim--Slim is a quiet leader. He does not desire attention, but he commands respect because of his discretion, tolerance, and kindness. He gives Lennie a puppy, offers a puppy to Candy to replace his dead dog, and provides comfort and advice to George. He is the only "pure" character in the novel.
Boss--The boss remains nameless and aloof throughout the book. Steinbeck chooses to portray him in this manner to show the alienation between the migrant workers and those in authority.
Crooks--Crooks is a black stablehand. He is completely isolated from the other men and lives in the barn. Steinbeck demonstrates what loneliness and racism can do to a human's soul. Crooks has become thoroughly disillusioned with life because of others' treatment of him.
The setting is Soledad, California, on the Tyler Ranch during The Great Depression. The individual chapter settings come full circle by the novel's end. The first chapter is set near the river, the second and third in the bunkhouse, the 4th and 5th in the barn, and the sixth at the same spot near the river.