jtsoundtech:
At this point, I haven’t yet been able to figure out just what means the original engineers used in order to accomplish this, but I’m very curious. Any insights that you can offer would be greatly appreciated.
I thought that most of these things were glove puppets. I remember reading that Gerry Anderson used a novel approach which he called 'Supermarionation' and I have the idea that involved voice activated mouths, but I don't know any details about how that worked. Perhaps with modern technology you could implement something similar?