Marble mini-game. If you want to unlock this mini-game on an Mdisk, you have to collect 88 Pearls.
Animal Mdisk. To unlock it, you should photograph all animals.
Bonus sequence. If you want to unlock it, all you need is to complete the game successfully and watch the credits without pressing any key. If you are patient enough, you will see another FMV sequence to start after the end of credits.
Beluga spaceship. To unlock it, find the codes which are on the bottom of the Jet Boots. You have to choose and rotate them.