Just a minor tweak on the very cool Artculated Slug by 8ran. I used Tinkercad to scale it up a little bit and add sockets for standard googly eyes. The ones I used are 6mm in diameter and it was a tight fit.

Everything is extra fun with googly eyes! :D

For best effect use 6mm Googly eyes like these Amazon affiliate link

Or these from AliExpress affiliate link