Puppet's with no soul.

It's tough to bring a puppet to life. A good deal of the illusion comes from the animator's performance and an engaging narrative, while some believability stems from the puppet's design. The better the design, the more fluid and natural the movement. The smoother the movement, the more life-like. But is 'life-like' the goal?
I'd argue that 'magic' is the goal. Something more than realism (otherwise you should simply film live action.) Somehow, it's a balance between the familiar and the unbelievable. It all comes down to a 'suspension of disbelief.'
From the start, Chuck and I agreed that our puppet's eyes needed to be as expressive as possible. We put so much weight on them, that at one point we removed them all together and opted for a hollow face. When we finally came around, Chuck found an old man who hand crafted glass eyes for dolls [contact information to be added.] As a finishing touch, Chuck added a little drop of lube which gave a great deal more depth to Mawk.
As an example of going the full distance, take a look at Chris and Maciek's film "Madame Tutli Putli" to see just how powerful eyes can be alongside skilled animation.