Chris at PyroElectro created a tutorial on building your own animatronic eyes.

One of the holy grails in animatronics is a realistic robotic eye because eyes are one of the hardest facial features to duplicate with realistic quality. While I have no intention of building the perfect animatronic eye in this tutorial, the low cost and convincing illusion created is rather remarkable.

This tutorial will present a single method for controlling 2-axis of robotic eye movement using an improvised gimbal system. This will give us control for the animatronic eye to move up and down as well as left and right, just like a human’s eye. Four micro Servo Motors will be used to acuate these movements in the eye.