The movie adaptations of Lord of the Flies show Simon playing with a lizard. It was considered his "pet" in both versions. It is unknown what happened to the lizard in the 1963 movie adaptation, but in the 1990 version, it was killed by Roger and Simon still kept its carcass. The 1990 movie adaptation revealed that the lizard was a chameleon.
I know. I'm horrible at drawing animals. That's why the lizard's face looks kind of dead.