The human characters are hand-drawn. John Silver's mechanical arm and the robot B.E.N. are flat-rendered CGI. The ship was created using Disney's 'Deep Canvas' process. In some scenes, all 3 types of animation appear simultaneously.
A sequel was planned with Willem Defoe set to voice the villain. However due to the original film's poor box office results it was cancelled. Defoe was not forgotten at Disney however and was later cast as a good guy in Finding Nemo.
When Jim and Dr. Doppler arrive at the space-port they get directions from two characters using a ladder. These are caricatures of the two directors: John Musker (at the top of the ladder) and Ron Clements (holding the bottom of the ladder).
The first Disney film in which the maquettes (small character reference sculptures) were not made entirely by hand, out of clay. Silver's cyborg parts were constructed out of plastic, using laser technology.
The trivia items below may give away important plot points.
At the end of the film, Dr. Doppler and Captain Amelia (two aliens) got together and had children. A few lines cut from the film revealed that Dr. Doppler (the male alien) gave birth to the children. Disney ordered the lines cut because they thought males giving birth, even male aliens, was too risqué for a children's movie.
Jim's clothes become lighter as the film progresses, symbolizing his transformation from 'bad boy' to 'hero'. Near the beginning, he wears a black T-shirt. During his adventure towards and on Treasure Planet, he wears a tan shirt. In the final scene, he wears a white military uniform.
The song "Always Know Where You Are" was written by John Rzeznik, who also performed the song during the end credits. However, on the soundtrack album, the song was performed by the British boy band BBMak.