Kurgan said:
I remember hearing sometime in the 1990's how they had locked James Earl Jones in a room with a microphone to record all the possible Vader dialog for the prequels and that they had five full minutes of tape.
Sounds kinda far-fetched to me. If it's true then if must have happened after some elements in the prequels (like Padmés name and - possibly - her death) had been finalized.