What did the rabbits symbolize?
In Of Mice and Men, the rabbits are a feature of George and Lennie's dream to own their own ranch and live off the land. As such, the rabbits represent economic freedom and their hope for a better life together.
For Lennie specifically, the rabbits also function as a symbol of happiness. Notice how he often he talks about tending to the rabbits on his dream ranch. For him, the rabbits are a symbol of comfort and pleasure.
At the end of the novel, just before Lennie's death, he has a vision of a giant rabbit. It says to him that he is not "fit to lick the boots of no rabbit" and that George will never let him tend any rabbits because of the bad things he has done.
This vision is significant because it suggests that George and Lennie's dreams will never come true. No matter how hard they try, they will never be able to escape the harsh realities of their existence and buy their own piece of land.