Pig

Pigs are animals that have appear throughout the Mario series, but unlike their real world counterparts, Pigs are often shown to be anthropomorphic or capable of speech.

In Paper Mario: The Thousand-Year Door, Doopliss turns the citizens of Twilight Town into Pigs with the ring of a bell. When Doopliss is defeated, everyone is turned back. The title of the chapter in which these events take place is called "For Pigs the Bell Tolls", which is a reference to the novel written by Ernest Hemingway called For Whom the Bell Tolls.