Big Time "Episode 3" spoiler folks, as revealed by James Earl Jones (the voice of Darth Vader). If you’d rather not know, don’t click through. Thanks to the guys at TheForce.net for this one.
When asked about Episode III, James Earl Jones talks about his role being about 5 minutes in length, right after Anakin goes "bionic" and falls into a volcano.
You can listen to the whole revelation here