Gold Shell

A Gold Shell is a very rare type of Koopa Shell, that seems to be so rare it only appears in two galaxies of Super Mario Galaxy. It only appears in the levels "Passing the Swim Test" and "Bigmouth's Gold Bait".

When Mario arrives he learns that the black Penguin gave his students a "Swimming Test" where the students have to find shells. The penguin that finds a Gold Shell instantly gets an "A" score. When Mario dives underwater he sees that a penguin has already found a Golden Koopa Shell and it is also the last and only one there is.

Mario swims up to the penguin who says that he won't give Mario the shell. However, Mario rudely takes the golden Koopa Shell from him and takes it to the black penguin. The penguin is impressed, so impressed that he gives Mario a gold medal (actually a star).

The penguin then realizes that Mario is not a penguin and starts wondering if Mario really is one of his students. After Mario got the gold medal, he will have to leave the golden Koopa Shell behind.

In "Bigmouth's Gold bait", Mario finds a golden treasure chest that will only open if he brings back a Gold Shell. After swimming through a dangerous cavern in the darkness, Mario found the shell and brought it back up, where it opens the chest, letting a Toad inside free, who gives Mario the star.