Yeah, I know it's a bit late to post this here, but hey it's worth it!! those of you who have the game, this is for you.
Here's some cheats:
Unlockable: The Zoo
You must collect 31 Gold Medals.
Unlockable: Somebody to Love
You must collect 12 Gold Medals.
If you are stuck(many of you may not be since it's an old game)just post it here and I'll be sure to help.