A key event in the life of Crooks in Of Mice and Men is when, for the first time, he pushes aside his personal prejudices, his dark preconceived notions, and the overall anger that he feels on a daily basis and seems to "buy in" the dream of Lennie, George, and now Candy, to have a farm where they all can live in.
This is a complete detour from Crooks's usual behavior, which denotes that the idea of the farm that Lennie and George hold so dear has definitely touched a nerve. This means that, somewhere in the depths of his mind, Crooks must have a very akin feeling that is awoken when he sees that, despite of it all, George and Lennie still dream--and now Candy seems to have the money to make that dream come true.
Being that Crooks is the only black man in the barn, he has an excuse to remain isolated. The novel is set in a time where racial differences were deeply set and social expectations rendered that someone like Crooks would have a hard time mixing with others.
However, it is during an unwanted visit from Lennie, and as Candy comes in afterwards, that Crooks learns that George, Candy, and Lennie had been planning about buying a farm together and living off it, ending once and for all their miserable lives as farmhands working for Curley.
Crooks does his best to mock most brutally the dreams of the men. This is perhaps the moment when Crooks is the most brutal and mean in his life. He is determined to crush the other men's "moment", and he is going hard at it. Yet, Candy discloses that there is money now, and that the plan can be carried on right away.
We gonna do it now, and don't make no mistake [...]money's in the bank
With this disclosure, Crooks realizes that the men are on their way to something that he, himself, wishes desperately from the depths of his obscure heart. This is very telling, and is reflected in Crooks's immediate change of attitude. So humble he suddenly becomes that he even offers his own warm body to work as a farmhand for them....for free!
If you[...]want a hand to work for nothing--just his keep, why I'd come an' lend a hand
This event is significant for the novel, as a whole, because it unveils that all of the men in the ranch may be very well just like Crooks: dreamers trapped in enslaved bodies. Men who have feelings and emotions just like everyone else, who also wish for their American Dream, who long to have a land to live off, and whose rogue mentalities are a consequences of their rough lives, not indicators of their personal characters.
This is the essence of the novel: the quest for a dream despite of circumstances; despite of fate. Everyone is entitled to try, and that is the beauty of the American lifestyle. Not all will get it, but everyone should have the same opportunity in this land. Crooks, Lennie, Candy, George, and even Curley's wife, all denote a want for something better for themselves. Everyone has a dream that lies deep within their hearts, even under the guise of roughness, rudeness, overt flirtation, weakness, or strength.