Super Mario Sunshine Easter Egg - Secret Book

To get to the level where the egg is, you must have Noki Bay, level 3 unlocked.

On level 3, 'Red Coins in a Bottle', Mario will jump into a bottle floating into the sky. Float all the way down to the stone structure at the bottom of the bottle. Move around to the back of the structure. You will see two squares cut into the rock. One of the holes contains a door. If you go into first-person camera mode using the control stick, and manuver it just right, you can see a book sitting behind the door.

The door is not openable by conventional means. The book was part of the Japanese edition, in which the old man sent you into the bottle to retrieve the book, and bringing it back to him earned you the Shine Sprite. However, the English version features a somewhat crappy door, olny to block it off; instead of re-configuring the entire level, they just added a door. The book says something in Japanese, translated loosely to "You have no life. Signed, Shigeru Miyamoto."