I was inspired by a NXT robot called RoboDog to build a four-legged critter. I ended up building it without the NXT, but I it still came out cute. I used the Power-Functions battery box and receiver, as well as a Power-Functions motor to rotate the head. But the legs are powered by an RC Buggy 9V motor, which is connected to the Power-Functions receiver by an extension cable. Click the picture for a video.