Fobots

Fobots!

From the website:

Each Fobot is numbered, with a copper plate on its back bearing the word "FOBOT" and its individual number. We call them butt tags.

Warning: Fobots are not toys, they are not functional, and they will not go on a rampage while you sleep. May contain lead solder (duh!), so don't eat them.

You can see our Fobots here.