Series 12 (2008) saw the introduction of CGI effects (provided by HiT Entertainment's subsidiary Hot Animation), with the intent of producing the show entirely in CGI the following year. The traditional models and sets were still used, but with computer animated faces superimposed on the models to allow for changing facial expressions. Humans and animals were fully computer animated to allow for walking movement. Only twenty episodes were produced and broadcast (the U.S. broadcast featured six additional episodes from "Engines and Escapades"). Sharon Miller became the head writer, starting with Series 12.