The Secret Origin of the Rust Monster
This metal-eating-armadillo-trilobite is a staple monster of the "Dungeons and
Dragons" roleplaying world, but like several other creatures from the original
game, it was shamelessly stolen from a generic, plastic toy:
Lord knows why, but this and other fictional creatures were once commonly
included with bags of cheap, plastic dinosaurs from Hong Kong, and such a
bag was used by game designer Gary Gygax in the earliest test-runs of his
infamous creation. The dinosaurs can still be found in dollar stores to this
day, but the original "Rust Monster" has become rarer and rarer.

And it doesn't end there!