Kingfin

Kingfin is a boss in  Super Mario Galaxy. It 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 can make robotic fish that look like it come from the core of the planet that work almost the same as Bullet Bills, chasing Mario down from all directions. The more damage Kingfin takes, more of these smaller robotic fish will come from the crator in the center of Bonefin Galaxy.

Trivia

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