How do I import a default character mouth set onto a different character created from scratch in illustrator.
If there is a mouth set in one of the sample puppets you like, that uses illustrator is easier, load up the puppet and select Edit Original from the menu to open it in Illustrtor. Expand the layers to find the Head / Mouth group. It should have Neutral, Ah, Oo, etc underneath it. Select the Mouth layer and copy it. Go over to your artwork and paste it inside Head. It should start working!
The only tricky things are if cycle layers are used, you need to add a cycle layers behavior per group that has image layers in it called 1, 2, 3 etc. Also, you will probably need to resize and move the mouth artwork. Before you move and resize anything, make ALL the layers visible for the mouth. It will look a mess. But then select the Mouth layer and move and resize it, then hide all the child mouth layers except neutral. If you don't do this, all the hidden layers will not be moved or resized and you have to do them one by one - much easier to make them all visible and resize/move together in one hit.
In addition to what Alan said, I have found that some AI mouth shapes are simply an AI's intrepation of a PS mouth. Take the time to examine the bezier curves on each mouth shape. Yep, it's a pain. But if you intend to use this mouth shape over and over, then your time to examine each shape, and simplify the bezier curves will be rewarded many times over. Be well fellow puppeteer. - Platty