Dawson Casting: Pazu and Sheeta (both at approximately 13-14; it's never stated in the movie) are voiced in the Disney English version by (fittingly enough) James Van Der Beek (21) and Anna Paquin (17), and sound considerably more mature than their intended ages. Longtime fans of the original Japanese version have stated this as a point of contention, while others don't find it so distracting.
Ironically enough, in the Japanese version, Mayumi Tanaka and Keiko Yokoyama, both who were in their thirties (as were Barbara Goodson and Lara Cody from the dub from the 80s Streamline release, at 38 and 30, respectively), portray Pazu and Sheeta as high-pitched-sounding kids. It remains debatable over who's performance of these two characters are preferable.
Genius Bonus: The 1964 black comedy film Dr. Strangelove also contained a ragtag bunch of misfits in a plane trying to reach Laputa (in Russia) which was also the location of a Doomsday device, a comically-over-the-top choleric general, and a mad scientist with dark glasses who was hiding his allegience to a defunct evil empire behind an assumed name.
For the Disney dub, veteran voiceover Jim Cummings plays the Army General, which incidentally is not too different from his voicing of Razoul in Aladdin. Creator.Tress Mac Neille also has a brief cameo, while Mike McShane plays one of Dola's sons (as do Mandy Patinkin and Andy Dick). John DiMaggio has a minor role as a army soldier as well. The best known voice over is Mark Hamill who plays the antagonist, Colonel Muska. His performance, along with Cloris Leachman's Dola, is considered one of dub's greatest assets. Anna Paquin also voices Sheeta.
In the Japanese version, Mayumi Tanaka as Pazu. Seems appropriate, considering Pazu is one of the closest things to a typical Shōnen hero you'll find in a film by Studio Ghibli.