In the poem To A Mouse by Robbie Burns, the main character is a mouse who is comfortably set in a human home, inside a hole and has to come out of it to get his crumbs to eat. However, he gets detected by the owner of the house and freezes. In the poem, the narrator tells the mouse not to worry, for he will not hurt him. After all, what harm could a mouse do when it has the same right to live its life the best way it can. True, a mouse can be considered a pest, and a rodent, and all that, but the narrator of the poem promises the mouse that it won't hurt it, in fact, if he could he would help him.
Lennie is like the mouse because he is actually (and sadly) a social nuisance. Like a mouse, he cannot be trusted, he causes havoc wherever he goes, aggravates people, and is in a place in society in which he is at the bottom of the totem pole. He was dependant on George because he was too mentally incapable to be independent, nor make a good life for himself. However, this does not mean he does not have the right to do it. After all, isn't he a human being? Aren't we all give the same free will? Yet, society has isolated him for his mental handicap and George for his protection of Lennie. The two have wishes together, but they are hard to come by, in fact, impossible. And nobody is there to provide them with any mercy either.
Lennie is simply a continuous thorn on George's side as much as he truly wishes the best for Lennie. However, when it comes to the social ladder, those at the bottom (like the mouse is in the food chain) are more prone to be wiped out by the big guy. And that is what happened to Lennie.
Regarding the poem "To a Mouse" by Robert Burns, Thomas Carlyle writes that Burns is "brother and playmate to all nature." That Lennie Small of John Steinbeck's Of Mice and Men is a brother of nature becomes apparent to the reader early in the novella as Lennie drags his feet like a bear and "dabbed his big paw in the water" before he drinks. And that the mouse is terrified by man as he is in Burns's poem is also evident as the mouse that Lennie hides in his pocket has died, probably from fear just as the little "beastie" has "panic" in his "breastie."
Of course, the greatest parallel between the little creature of "To a Mouse" and Lennie Small, who is, indeed, but a small man in the scope of the many disenfranchised itinerant men, is that like the Burns's mouse he falls victim to "Man's dominion." For, with Lennie's diminished mental capacity, he has only a small place in the fraternity of men. And, with his misfortune in killing Curley's wife, he is doomed to be destroyed and, with him, so is the "nest" of the dream of a ranch that he and George have--"Thy wee-bit housie, too, in ruin." Now, the mouse is faced with "bleak December winds ensuin'" just as George, after Lennie's death, is faced with the terrible aloneness and the death of their dream with which he is left. With both the "wee" mouse and with Small, the schemes of Mice and Men do, indeed, go awry.