Marble Mini-Game:
Collect 88 Pearls to enable the Marble mini-game on the Mdisk.

Animal Mdisk:
Photograph every animal in the game.

Bonus FMV:
Beat the game and watch the credits. During the credits, don't press any buttons and when the credits end another FMV will start.

Unlock the Beluga:
The codes on the bottom of the Jet Boots unlock the Beluga Spaceship. Simply rotate the boots to see the codes.

Thanks to Revolution reader Kalib, Mopants, and DucatiXR!