Trekkie Monster said:
I did know that they are bunraku puppets, but it seems to me that the sloth and the turtle are full body costumes (a la Bear) It was apparent with the buraku other puppets where the performers hands went into the sleeves to operate the hands
I think that with the use of green screen, there is the option of having another puppeteer operate the other arm. Even with a full body puppet like the sloth.
I didn't know they had another full body puppet (turtle). I just looked up the characters, if you mean Madge, I always thought she was a stadard bunraku/hand puppet. Are you sure that she is a full body puppet? Either way, depending on the actual shot you saw, you should ask youself "Could there be puppeteers in green suits anywhere in this shot?".
Also remember that there is the option of post production to eliminate any puppeteer arm that might have gotten into the shot (like with removing rods in post).
Is the shot you are talking about (the back of the head) a static shot with the sloth dancing? Or was the shot a pan/rotate from the front to the back of the puppet? This will help you figure out how they were able to make it appear like the puppet was fully alive.
*Disclaimer* I am by no means trying to sound like I know how this stuff actually works. I am just using my approximate knowledge to try to make sense of what you are describing and offering my thoughts.