One thing I've learnt is that trying an idea out in card using split pins for joints really helps visualise the end product. I've then moved onto making a simple version using florist wire (you can see this in the head mechansism). As you can see this is a bit of a rough version but it does work. I can now rework it to improve strength and smoothness of movement.
One thing I am pleased with is the change in speed from the wheel spinning in the background to the gentle left to right head movement. That was a total flook!
Saw a great quote from the director of Toy Story 3 who was discussing the experimental approaches they use to create Pixar movies: "Screw-ups are an essential part of making something good. That's why our goal is to screw up as fast as possible"