Having been disappointed by the generic offering of Christmas lights with small customization options, he decided to make fully customizable light decoration.
Small PIC12F609 MCUs along with RGB LEDs are placed on a board and daisy chained over a 3 wire cable. A master MCU is placed on one end of the cable and controls the color of the lights individually by sending addressed data over the wires. [via]
Christmas lights with a MCU in each bulb - [Link]