First, Santa is now bobbing to the guitar playing of Elfis (instead of shaking his head in disapproval).
Arduino files have been added (on this site) to reflect this change. The dog now moves his head--left, right, up, down at random time intervals and random positions.
A vexing problem that took a few days of troubleshooting to fix started when the ferris wheel was converted from manually switched battery power to wired "wall wart" power. Electrical noise caused the monkey to vibrate (noise on the servo motor) whenever the ferris wheel was switched on (by relay). I tried a "junk box" capacitor across the ferris wheel motor, but the problem continued. Somehow, the three feet of twisted wire supply was radiating noise. I tied a resistor to the servo signal pin; I pulled the pin low during ferris operation--nothing helped. Finally, I ordered a .1 microfarad capacitor and soldered it across the ferris wheel motor leads--problem solved. Who knows what value my "junk box" capacitor was, but it didn't work.