How are Lennie and George different from other people on the farm?

Lennie and George share a firm and lasting friendship and this state of companionship sets them apart from the other men on the ranch. 

The job of being a ranch hand entails a considerable amount of movement for many of the men, forcing them to travel to find work. In addition to a rather solitary sensibility that functions almost as a (masculine) code of values, the prevailing conditions of farm work during the Great Depression in California presented in the book serve to isolate individuals from one another.

There is a notable lack of friendship -- lasting or otherwise -- among the men on the ranch. Slim is admired, but holds himself somewhat aloof. Candy is very nice and friendly, yet until George and Lennie arrived he seems to have had no actual friendships on the ranch.

Added to the isolation produced by migratory patterns and a stoic social code, there are also class and race differences that keep people divided. Curley has no friends in part because he tries to maintain a class-based distance between himself as a representative of ownership and men who labor on the ranch.

George and Lennie defy the odds and maintain a remarkable friendship. The fact of this friendship makes the pair different from the others on the ranch.  

"If them other guys gets in jail they can rot for all anybody give a damn. But not us.”

Lennie broke in. “But not us! An’ why? Because…because I got you to look after me, and you got me to look after you, and that’s why.” He laughed delightedly. “Go on now, George!”

The stability of this friendship may be partly responsible for helping George and Lennie forge a shared dream as well wherein they will have a stake in their own labor by taking ownership of a small farm of their own. 

George and Lennie are conscious of their special status as men with a social network, however meager it may appear to the reader. Others are equally aware of this difference in the pair and this awareness is noted throughout the novel by the boss, Candy, Slim and others. 

More than any other elements of their characters, it is the friendship shared by George and Lennie that makes them different from the others on the ranch.