A box of replacement hands.

A box of replacement lips.

In order to express the puppet's emotion and facial well when it is animated, I made up a box of replacement lips. I only need to exchange one lip for another during the animation process. Everything in clay animation takes so long, any device can save time is more than welcomed.
Actually, there are 2 most common ways are used. An old fashion is to make up a set of replacement heads. Some artists prefer to work with this method that remains a unified entity, and probably has less variation in skin tone. The other way is to make up a series of replacement mouths. Make sure the joints do not show when the mouth is modeled in.