George Lucas deliberately made the Darth Vader suit top-heavy (for instance adding weight on the helmet) to make Hayden Christensen not appear "too accustomed" to it in the movie.
The original cut of this movie ran nearly four hours. The opening battle/Palpatine rescue alone ran over an hour. The extra footage of the Palpatine rescue scene is shown in the video game for this movie, however.
The images of the volcanic eruption on Mustafar is real footage of Mt. Etna in Italy, which was erupting at the time of production while the crew was filming backdrop photography in Italy for the movie, per Lucasfilm editor J.W. Rinzler's book The Making of Star Wars: The Empire Strikes Back.
Ewan McGregor and Hayden Christensen trained for two months in fencing and fitness in preparation for their epic battle. As a result of their practice, the speed at which Kenobi and Vader engage the duel (in the completed movie) is the speed in which it was filmed, and was not digitally accelerated.
Chancellor Palpatine's strategy for maintaining power is known to political scientists, and is called Perpetual War. He comes to power through conflict with the Trade Federation, gains greater privileges through the Clone War, and solidifies his position through war on the Jedi.
Jett Lucas: The young Jedi who rushes from the Temple towards Bail Organa's speeder during the Jedi Purge is played by George Lucas' son.
Nick Gillard: Stunt coordinator as Cin Drallig, a Jedi Anakin kills in the video recording Obi-Wan watches.
George Lucas: The blue skinned Baron Papanoida who appears just outside the entrance to Palpatine's private box at the Galaxies Opera House.