Kingfin

Kingfin is a boss in  Super Mario Galaxy. He is a giant skeleton fish, living in the Bonefin Galaxy. To defeat it, Mario must take Koopa Shells, and throw them into Kingfin's interior.

Kingfin has smaller versions of himself that work almost the same as Bullet Bills, chasing Mario down from all directions. The more Kingfin is hit, more of these smaller fish will come from the creator in the center of Bonefin Galaxy.

Kingfin is so strong, that over the course of the level, he can destroy the pillars and rock formations that surround the watery planetoid.

Trivia

 * Kingfins's name is a pun on the word "kingpin," which means: "The most important person in an undertaking or organization".