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 the player arrives he learns that the penguin's Coach 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 the player 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.

the player swims up to the penguin who says that he won't give them the shell. However, the player can take the golden Koopa Shell from him and takes it back to Coach. The penguin is impressed, so impressed that he gives Mario a gold medal (actually a Power 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", the player 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, the player find the shell to bring back up, where it opens the chest, letting a the Captain of the Toad Brigade free. He gives Mario a power star for rescuing him.