I think that one of the most direct similarities between all four of these characters is that they are all trapped in their world. Each of them cannot escape the pressures of the world that are weighing on them. Candy's dog is helpless to stop his own execution. Candy, himself, is helpless to do anything to either save his dog or to make his own life better. Lennie is helpless in terms of being completely dependent on George and unable to actively construct his own world in accordance to his dreams. George is unable to repel the force of the world and must, in the end, do what it is he does not want to do in killing Lennie. Each of the four characters cannot repel the pressures of the world that are bearing down on them in a high level of force and magnitude. In this, they are all trapped and crushed by the weight of the world that is bearing down upon them. They are incapable of finding lasting happiness in a world that is extremely unforgiving and driven to weed out those who are weak or perceived as weak, lacking power or autonomy over their own lives. It is in this element where the four characters share another similarity in that they lack a sense of determination and autonomy over their own lives.