Don't let the name fool you: Lennie Small is big. Unfortunately, that's about all he has going for him—that, and he's got a really good friend. So, what did Lennie do to deserve a friend like George?
Lennie and George
When we first meet Lennie and George, we almost can't tell them apart: "Both were dressed in denim trousers and in denim coats with brass buttons. Both wore black, shapeless hats and both carried tight blanket rolls slung over their shoulders" (1.4). They're two itinerant farmworkers, looking for work wherever they can. From a distance, there's nothing to tell either apart. But when we get closer, we see that this isn't a relationship of equals:
Lennie, who had been watching, imitated George exactly. He pushed himself back, drew up his knees, embraced them, looked over to George to see whether he had it just right. He pulled his hat down a little more over his eyes, the way George's hat was.(1.10)
If this reminds you of a kid imitating his dad, then you're on the right track: from these few sentences, we know that something is seriously wrong with Lennie. Like a kid, he mournfully wishes for ketchup to put on his beans; like a kid, he demands a bedtime story—even when he knows it all himself: "No…you tell it. It ain't the same if I tell it. Go on…George. How I get to tend the rabbits" (1.121).
We don't know exactly what the problem is, but we know that Lennie has a serious mental disability. He can't remember anything; he fixates on things like owning rabbits; and he's painfully eager to make George happy. He even gives away all of the (imaginary) ketchup: "But I wouldn't eat none, George. I'd leave it all for you. You could cover your beans with it and I wouldn't touch none of it" (1.93-95).
This still doesn't help us figure out why Lennie gets a friend like George. In fact, it seems like Lennie shouldn't have many friends at all—even George thinks he's a little annoying. Lennie almost gets it: "I got you to look after me, and you got me to look after you" (1.115). What…