Why Did the Cyclops Close His School? Because He Only Had One Pupil
Only Kevin Khatchadourian would do something involving his sister and Liquid Plumr, causing her to permanently lose an eye. And only Kevin Khatchadourian would then kill his sister by pinning her to a tree with arrows, then take her fake eye from her dead body and keep it to taunt his mother. "It isn't often that when you look at an object, it looks back" (28.21), Eva tells us. Yikes. The eyes have it: this kid is evil.
But like every object in this book, the eyeball can continue to be analyzed. When Celia is having the eyeball made, Eva wants glass, but Franklin wants it to be a polymer. "I hate plastic" (24.19), Eva says. Considering Kevin calls Franklin "Mr. Plastic," this short sentence definitely has a double meaning.
We also get an early glimpse of how Kevin is using the eye incident to torment Eva. He knows Celia is her favorite, and Kevin will do anything to destroy a person's favorite thing. After Celia loses her eye, Kevin rubs it in by peeling and eating lychee berries in front of Eva. Yeah, for your next Halloween party, peel some of these, blindfold your friends, and tell them they're eyeballs.
Despite Kevin's cruelty—like when he shows Eva the eyeball while he's in jail (how did he get it into the jail in the first place?!)—when Eva tells him never to show it to her again, he doesn't. And when he's about to be transferred, he gives Eva the eyeball to bury. Once again, we have to wonder, is it a peace offering? Is Kevin truly sorry? Or is he just trying to get on his mother's good side because she's all he has left?