World S

"Wow! Can ya believe it?! This must be that strange, legendary world we've been hearing rumors about! There are even more Power Stars around here! So! Let's go get 'em, Captain!"

- Lubba

World S: Here We Go!, also known as Special World, is the seventh and last world featured in Super Mario Galaxy 2. It is located high in the sky of an unknown planet with colorful star-shaped islands, and has two rainbows in the background. This world is shaped like an "S", hinting at its name, and has no forked directions. It holds a total of seven galaxies, the last of which, the Grandmaster Galaxy, can only be accessed by collecting all 120 Power Stars as well as all 120 Green Stars. Each galaxy is blocked by a star barrier (the most out of all worlds) that requires a certain number of Power Stars to unlock rather than simply completion of the previous galaxy. The world is unlocked after the player completes Bowser's Fortified Fortress for the first time. This is the only world in the game to lack any hidden stars, with each galaxy featuring one main mission, one Prankster Comet (with all types except for the Romp Comet present and also the most comets out of all worlds), and (excluding the Grandmaster Galaxy) two Green Stars.

This world's appearance is hinted at by a Bob-omb Buddy brought back from the Throwback Galaxy, who asks about the "strange, legendary world" in a manner similar to Lubba's. This world's music is a slower rendition of Gusty Garden Galaxy's music from Super Mario Galaxy.

All of the galaxies in this world except for Flip-Out Galaxy are references to previous Super Mario games. Mario Squared Galaxy, Stone Cyclone Galaxy, Boss Blitz Galaxy and Grandmaster Galaxy (in the case of The Perfect Run, because of the music) are references to Super Mario Galaxy, Rolling Coaster Galaxy is a reference to the Rainbow Road courses from the Mario Kart series and Super Mario 64 (because of the music), and Twisty Trials Galaxy is a reference to "The Secret of Ricco Tower" from Ricco Harbor in Super Mario Sunshine.

Trivia

 * This is the only world in the entire game where every galaxy has two regular missions, and all but one have two Green Star levels.
 * None of the galaxies in this world has a teleporter that leads to a Bonus Planet.
 * During the introduction cutscene, Mario can be found as a little dot right next to the Boss Blitz Galaxy.