This is not really an Instructable as such. I intend to just give you some guidelines on creating a version of the awesome project using a vintage Teddy Ruxpin and the C.H.I.P 9 dollar microprocessor.
The Robot Head speaks any text that you type into the web page that it serves up. All you have to do is type the web address into your browser and the page appears. The C.H.I.P. microprocessor receives the text via wifi and runs it through a text to speech converter. I also added a random function that quotes Albert Einstein occasionally. Led lights flash, the eyes move, the mouth is automatically synched with the speech. It's really cool...and a little creepy.
If I were you, I would begin looking at the Chippy Ruxpin info from Make Magazine: http://makezine.com/projects/chippy-ruxpin/
I was really inspired by the article. I ordered the C.H.I.P. and patiently waited for a couple of months for it to arrive. I followed the instructions in the Makezine article, and it all worked without a hitch.
http://www.thingiverse.com/thing:1351302 - Dasaki Compact Animatronic Eyes
http://www.thingiverse.com/thing:402281 - Eyelid I adapted to the Compact Eyes
Previously, I took the Dasaki Compact Eye 3D model and altered it to use a universal joint for the eye movement and full upper eyelids. I re-designed the eye support bar as you can see in the image. The green piece is my revised version.
I also adapted the eyelids to the eyeball size. The 3D file is for ping pong balls.
I used a Traxxas 1539U-joint for the eye support. For the eyes, I got cheap Halloween mask half-eyes. They come in a bag with different colored irises. Some epoxy putty held the U-joint to the eyeball, and the other side was bolted into the eye support frame.
I attached a 9 gram servo behind each eye with an arm on it, and a thin wire going from the end of the arm to the connecting point on the eyelid.
BUT..... there are lots of YouTube videos out there with people showing eye mechanisms. Most use brass and wood and epoxy putty to create the moving eyes. You can use ping pong balls for eyes. You can use those plastic Easter eggs for eyes and size it up. Hobby stores sell clear plastic balls that split in half in various sizes.
Really, Why do the same thing I did? Why not try something different and outrageous?
For the jaw, I made a 4-bar mechanism. I have made these before with flat brass from the hardware or craft store. You could use popsicle sticks, or balsa wood, or any sort of plastic. The mask's chin is really lightweight, so it doesn't take much to move it.
Instead of a 4-bar mechanism, you could use a simple lever and so the jaw moves in an arc instead of a linear movement. A servo could pull a string to move it down, and elastic could bring it back up.
The ears I created and 3D printed could be lids to a jar of peanuts. They could be cut from the bottom of a Coke plastic bottle.
The brain came from a group of spheres on Thingiverse. But you could use polyfill and insert leds to make it glow like a cloud. You could use a mass of twisted wires. Maybe a mobeus strip? A balloon paper mache'd with images of things it is thinking about? Bubblewrap?