I had a few more ideas:

• Palpatine: Execute order 64 -- no, wait -- 65? 67? Just wipe them out. All of them.
• I am not sure how often George is seen in the opera scene. If it's more than once he could change colors every time.
• Mace: I am Mace Zeus Windu.
  Palpatine: Zeus?
  Mace: Yeah, Zeus! As in, father of Apollo? Mt. Olympus? Don't f*ck with me or I'll shove a lightning bolt up your ass! (from Die Hard with a Vengeance)
• On Mustafar Kenobi bursts into song (I didn't watch Moulin Rouge for nothing):
  My gift is my song... and this one's for you
  And you can tell everybody that this is your song
  It may be quite simple, but now that it's done
  I hope you don't mind, I hope you don't mind
  That I put down in words...
  How wonderful life is, now you're in the world
  (Then Anakin goes: NOOOOOOOOOOOOOO!)

"-I'm definitely replacing Grievious' voice, just don't know with what yet"

How about Mark from 'The Room'?

Examples...

Sith Sidious: The end of the war is near.
General Grievous: You think girls like to cheat like guys do?

Anakin Skywalker: General Grievous... you're shorter than I expected.
General Grievous: As far as I'm concerned, you can drop off the earth.

That's a promise.

Obi-Wan Kenobi: We have a job to do, Anakin. Try not to upset him.

General Grievous: You're the cause of all of this. I don't love you. Get out of my life, you bitch!

Obi-Wan Kenobi: Hello there!
General Grievous: Oh, hey Johnny, what's up?

General Grievous: You don't understand anything, man. Leave your *stupid* comments in your pocket!
Obi-Wan Kenobi: Oh, I don't think so.

Aw nuts.

Who is Mark in ep 2?

Ah okay ^^

I wasn't sure if that voice was used or not. Jeez, I've been out of it for a little while, every voice gets delusions of grandeur!