The minor characters (characters except George and Lennie) highlight the themes of the story (the theme of barriers (freedom and confinement) and the theme of dreams) by creating tension and foreshadowing.
Here is an brief example of how minor characters highlight the theme of barriers:
Crooks and Curley's wife highlight the theme of barriers. Crooks is born black, so he faces discrimination and cannot have the same freedom as other characters even though he is knowledgeable. The recurring symbol of chain and harness emphasizes this fact, suggesting that he is just like a horse being controlled by a harness (which represents societal norms and limitations). For Curley's wife, she is trapped in her marriage as she doesn't like Curley, as shown by her confessions to Lennie. However, she cannot leave the ranch as women at that time were dependent on men.
Are there any more such examples (I know Candy can also highlight this theme as he is disabled and "crippled". Is there any way I can explore this in depth? Thank you!