Trivia: General Grievous is permanently coughing when he talks. The cause is revealed in the last episode of the animated Emmy-winning TV series "Clone Wars" (albeit technically no longer canon). In that episode, Grievous kidnaps Palpatine and before leaving, is attacked by Mace Windu, who destroys part of his chest armour, making him cough for the first time.
Trivia: George Lucas makes a cameo appearance during the opera scene. He is the blue faced being, named Baron Papanoida, that you see outside Palpatine's box. It marks Lucas' first and only appearance in any of the Star Wars films; also in that scene is Lucas' daughter Amanda and her boyfriend. Lucas also reportedly provides the sound of General Grievous' coughing.
Trivia: Hayden Christensen wanted to wear the Darth Vader suit in the films, as it had always been a dream of his (revealed in the DVD commentary). Though the filmmakers hesitated, as Christensen was too short, they eventually let him wear the suit onscreen, but Christensen had to look through the mouth-piece of the Darth Vader costume, not the eyes.
Trivia: The blue-skinned Twi'lek Jedi Aayla Secura, who can be seen in this film and "Attack of the Clones", was not created by George Lucas. She originated in the Star Wars comic books from Dark Horse. After seeing a cover painting, George Lucas became so impressed that he decided to use her in the movies.