In Noki Bay, once inside the bottle in the Red Coins in a Bottle level, Mario should fall to the bottom of the bottle and then locate a small rock formation there. If Mario maneuvers into a small square opening towards the back right of the rock formation, he can find a small door inside the opening which is impossible to open. Therefore, the player must rotate the camera to see what is on the other side of the door. In doing so, Mario can see a brown book on the floor of the room behind the impassable door, though its purpose is unknown.

The book itself may be a reference (or vice versa) to the level's background music. In the Original soundtrack, the title of the level's theme is in fact "The Book in the Bottle". It's also been said that this mission was originally different, and that Mario would collect the book rather than 8 red coins.

"Isle Delfino" is Italian and literally translates into "Dolphin Island", likely referencing Gamecube's original code name, Project Dolphin (abbreviated as DOL, and can be seen under every Gamecube).

In the Japanese version of the game, there are files referencing planned train stations and dialogue involved in obtaining and stamping tickets. Each ticket would take you to one of 15 stations.

In an early prerelease version of Super Mario Sunshine, Delfino Plaza has a different look than in later prerelease versions and the final product.

Il Piantissimo is actually The Running Man from The Legend of Zelda: Ocarina of Time/The Postman from The Legend of Zelda: Majora's Mask.