Yen Sid

Yen Sid is a master magician who made his Disney debut in Fantasia. He appears in Kingdom Hearts II as an aid to Sora and the gang. Apparently, he was the master of both King Mickey and Donald Duck. His name is two separated parts of the word 'Disney' backwords.

History
The great sorcerer first appeared in Fantasia as Mickey Mouse's master. He was the owner of a magical hat (which he wears in Kingdom Hearts II) that is apparently the source of his power. In the movie's most acclaimed song, Mickey steals the hat and begins to play with its magic. But, as he was warned by Yen, it goes out of control he cannot control the extent its magic. Yen Sid arrives and manages to stop the magical chaos with his own powers.

Kingdom Hearts II
Yen Sid serves as Sora's tutor to what lies ahead of him in his journey. He lives in Twilight Town in a large tower off the skirts of the main town. He dwells at its top, where he studies the Nobodies and Organization XIII. When Sora, Donald and Goofy arrive, he tells them of the enemies that they will face in the near future (Nobodies, Heartless and the Organization). He also returns to them their Gummi Ship and the co-ordinates to Hollow Bastion.