Rodman Philbrick's novel Freak the Mighty is one of my all- time favorite books! The story is told through the eyes of the narrator, Maxwell Kane. Kevin and his mom move in next door to Max and his grandparents, and an unlikely friendship is born.
One of the primary ways that Kevin changes is in his attitude toward Max. At first, he treats Max with something like disdain. He certainly adopts an attitude of superiority over Max. The first words he speaks to Max nearly scare the big kid away. When they meet in chapter two, Kevin begins the exchange:
"Identify yourself, earthling." I'm busy keeping my feet from tripping and don't get that he means me. "I said identify yourself, earthling, or suffer the consequences." I'm like, what? And before I can decide whether or not to tell him my name, or which name, because by now I recognize him as the weird little robot kid from daycare, and maybe he recognizes me as Kicker, anyhow before I can say a word he pulls the trigger on that crutch and makes a weapon noise, and goes "Then die, earthling, die!" I motor out of there without saying a word. Because I'm pretty sure he really means it. The way he points that crutch is only part of it. You have to see the look in his eye. Man, that little dude really hates me. He wants me to die.
Later on, in chapter six, Kevin realizes that he and Max can be really useful to each other, and that is when their symbiotic friendship is born. Kevin feels bold enough to insult Tony D. (a.k.a. Blade) and his gang because he is with Max, and he figures Max can beat them in a fight due to his size. When Max tells him that a person can't just fight Blade—they'd have to fight his whole gang—Kevin is amazed, and it becomes a bonding moment between the two. Max picks Kevin up on his shoulders, and Kevin is awed by the fireworks display in the park. When Blade and his gang come after the pair, Kevin directs Max where to go to evade the gang. This is how they become Freak the Mighty.
Kevin designs quests for them to go on that involve righting wrongs in the world. He is the brains of their partnership, and Max is the brawn. This brings about another change in Kevin. Whereas his world mostly consisted of his relationship with his mother and his own imagination before Max, with Max he has become braver and more outgoing. One of the ways he demonstrates this is in chapter twenty when he stands up to Max's dad. Max's dad has gotten out of prison and is holding Max hostage. Kevin comes to Max's rescue by telling Killer Kane that he got a squirt gun and a chemistry set for Christmas, and he points the squirt gun that he claims is filled with sulfuric acid at him. When he sprays the liquid at Killer Kane, the man begins screaming in pain, allowing the two boys to escape.
The other changes in Kevin are physical. He has a twisted spine, which causes him to not be able to walk normally. As Max says it, his insides continue to grow faster than his outside, which causes complications. He has a seizure and is taken to ICU and given a tracheotomy. He invents a story about an operation to get a new, bionic body, but later in the story, we learn that Kevin knew from a young age that he wouldn't live long. His friendship with Max gave him hope and a desire to live beyond the limitations of his physical body.