Kashyyyk is the heavily-forested planet seen near the end of Episode III: Revenge of the Sith. It was first seen when we see Yoda discussing issues with the Jedi Council while helping the Wookiees, the indigenous inhabitants of the planet. Before then, it has been mentioned numerous times in the Expanded Universe, and was originally going to be in Return of the Jedi and The Phantom Menace, but George Lucas decided that Endor and Naboo were better choices. Later, Kashyyyk is one of the places where Order 66 is first issued, and is the earliest point in the story where Chewbacca appears, according to the Star Wars timeline.