Because of the setting, the characterization of Crooks is meant to demonstrate the effects of racism and discrimination. He is physically isolated and lonely—he is not allowed into the bunkhouse with the other ranch hands. Curley's wife realizes the delicate position Crooks is in, and she uses his race against him, indicating that one accusation from her "could get [him] strung up on a tree so easy it ain't even funny." Crooks is intentionally isolated at the ranch and in society at large, and this creates a deep loneliness within him.
Because of the threats Candy's wife makes, Crooks is frightened into solitude. If he can't trust her, then he feels he shouldn't trust anyone else on the ranch, either. He tells Candy,
Maybe you guys better go. ... I ain't sure I want you in here no more. A colored man got to have some rights even if he don't like 'em.
Crooks doesn't like being so isolated, yet he also believes that there is safety in removing himself from the presence of white people. He turns to isolation and therefore loneliness as a means of protecting himself, but notes that he doesn't like it.
Crooks seems to find Lennie the least threatening ranch hand. When Lennie approaches him privately, it doesn't take Crooks long to warm up to the idea of friendly conversation:
Crooks scowled, but Lennie's disarming smile defeated him. "Come on in and set a while," Crooks said. "'Long as you won't get out and leave me alone, you might as well set down." His tone was a little more friendly. "All the boys gone into town, huh?"
Crooks typically tosses everyone out of his room, establishing clear physical boundaries. Yet Lennie's efforts to befriend him feel genuine, and Crooks softens to the possibility of engaging with someone else on the ranch.
In his conversation with Lennie, Crooks shares bittersweet memories of his childhood:
"The white kids come to play at our place, an' sometimes I went to play with them, and some of them was pretty nice. My ol' man didn't like that. I never knew till long later why he didn't like that. But I know now."
He hesitated, and when he spoke again his voice was softer. "There wasn't another colored family for miles around. And now there ain't a colored man on this ranch an' there's jus' one family in Soledad." He laughed. "If I say something, why it's just a nigger sayin' it."
Themes of loneliness have been woven into Crooks's entire life. As a child, he didn't know another Black family and played with white children, much to his father's dismay. His need for childhood friendship was great, and his sense of innocence prevented him from realizing the inherent dangers in such relationships. Now as an adult, he faces much the same situation, isolated because of his race. In these reflections, the pain of a lifetime of isolation and loneliness weighs heavily on Crooks.