I found this "making of" video for the animatronic baby here:
The Google-translated description from the video above says, "Miguelín embodies the dreams of a better future for cities." Sadly, I guess that means our future will be filled with giant robot babies.
Another making of video here, via io9:
The baby is apparently 6.5 meters tall, and made by Amalgamated Dynamics Inc. in Chatsworth, CA (USA).
This is about the 1000th cool thing I've heard about the Shanghai expo, a trip down there might be in order this summer.
More giant puppet things here.
(p.s. The post title of Giant Sized Baby Thing is a Bow Wow Wow song)