You probably noticed that Kenny's favorite toy is his collection of little plastic dinosaurs. He and Rufus play with them all through the book. But they don't just pretend the dinosaurs are dinosaurs. No, they pretend the dinosaurs are Nazi and American soldiers fighting battles in World War II. Okay, so what? Why does that matter?
Let's take a look.
When the book begins, Kenny is still a little kid. He has a vivid imagination, he plays with toys, and his biggest worry is getting picked on by the kids at school. Kenny doesn't really know much about the real world at this point. Example? Well, at the time, the Civil Rights Movement is a Big Deal all over the country. Sure, Kenny has seen a few pictures of angry white people on the news, but he doesn't really get what's going on.
And of course, it doesn't really affect him—as a kid in Michigan, he's still protected from it all. He doesn't have any grown-up concerns yet. In fact, he even tells Dad, "I don't think I'll ever know what to do when I'm a grown-up. It seems like you and Momma know a lot of things that I can never learn. It seems real scary" (9.32). And it is scary to be a grown-up, but Kenny doesn't have to worry about that just yet. He's still in dinosaur land.
Unfortunately, not for long. The Watsons travel to Birmingham, where it's much tougher to protect anyone from the racism and anger surrounding the Civil Rights Movement. Sure enough, some white men set off a bomb in an African American church, killing four little girls (P.S. real historical event alert!).
And suddenly Kenny is thrust into the grown-up world. He's no longer innocent and worry-free; now he has seen hate and violence up close. And boy does it change him.
Okay, but what does this have to do with the dinosaurs?
Well, the dinosaurs are symbolic of Kenny's change. In literature, we call this change a "coming of age," meaning a loss of childhood innocence and an introduction to the adult world. When Kenny gets home from Birmingham, he no longer wants to play games or hang out with his friends:
Momma started trying to force me to do more things with Rufus but it seemed like he'd changed while we were gone and wasn't as much fun to be with. Him and Cody got real happy when I gave them my pillowcaseful of dinosaurs. I was getting too mature to play with toys anymore. (15.23)
The fact that Kenny physically gives up his dinosaurs represents the giving up of his childhood. It's really Kenny who has changed—you caught that one, right?—and he feels too mature for toys. To him, toys seem silly and unimportant in the face of people being killed due of the color of their skin. He can't just imagine that away.
Kenny is so devastated about what happened (and maybe about the loss of his childhood) that he just wants to hide behind the couch. Just like he said to Dad earlier, it is scary to be a grown-up and to know grown-up things.
Fortunately, Byron is there to help Kenny out with this one. Byron explains that Kenny has to keep living; even though terrible things happen in the world and even though none of it is fair, Kenny can't hide out forever. And even though Kenny has had to face the grown-up world, he's still a ten-year-old kid, so to keep living means to keep playing games and hanging out with his friends.
In the end, Kenny decides he needs to get at least half of his dinosaurs back from Rufus. Sounds like a good idea to us.