There’s just one servo in the bear’s head to drive both the mouth and the eyes, so it’s not exactly rocket science to hack the bear—the main trick is synchronizing the movements with the processed text stream. The BearDuino sketch code drives the servo based on serial input sent from the PC, mapping the values to a range of 180 degrees of motion. (via BearDuino: Hacking Teddy Ruxpin with Arduino | Ars Technica)