mechanism

A mechanism (sometimes shortened to mech) is a device used to manipulate a puppet's movement. Mechanisms are often used by puppeteers to control secondary movements, such as blinking eyelids, raising or lowering eyebrows, and wiggling ears. Sometimes, especially when a puppet is particularly small or large, a mechanism may be required to manipulate a primary movement, such as opening or closing the mouth.

• Gonzo from the Muppets has a trigger mechanism to control his eyelids.
• Rizzo the Rat from the Muppets has a trigger mechanism to control his mouth because he is too small for a puppeteer's hand to fit into the head.