He is the leader of the mule team.
He is highly respected by everyone on the ranch including Curley.
He is tall, ageless and an expert in his job.
He is "the prince of the ranch", and regarded with authority.
He is the only one who realizes at the end of the novel, for the reason of George's decision.
He is reffered to as "the swamper".
He is an old man who lost his hands in a ranch accdident.
He owns an old sheep dog that gets killed by Carlson later on the novel, a symbol of Lennie's fate before the novel ends.
He is afraid that he will eventually get sacked, when he becomes useless.
He convinces George to let him join their dream of owning a farm.
The principal characters are George Milton and Lennie Small (whose name is the subject of a feeble joke: “He ain't small”. Who says this?).
Lennie is enormously strong.
He is simple (has a learning difficulty) though he is physically well co-ordinated.
He is capable of doing repetitive manual jobs (bucking barley or driving a cultivator) with skill.
Lennie has a man's body, but a child's outlook: he gains pleasure from “pettin' ” soft things, even dead mice.
He loves puppies and rabbits.
He is dependent, emotionally, on George, who organizes his life and reassures him about their future.
Lennie can be easily controlled by firm but calm instructions.
But panic in others makes Lennie panic: this happened when he tried to “pet” a girl's dress, in Weed, and happens again twice in the narrative.
Lennie's deficiencies enable him to be accepted by other defective characters such as Candy, Crooks and Curley's wife.
He poses no threat, and seems to listen patiently (because he has learned the need to pay close attention, as he remembers so little of what he hears).
As a child is comforted by a bedtime story, so is Lennie and has to be comforted with a tale of a golden future by George.