Giant Worm (Samurai Jack)

The Giant Worm is a two-headed worm-like sea monster that appears in Samurai Jack, Episode XV: Jack Tales.

History
The worm is black and red with gill-shaped ears and blank white eyes. When Jack traveled to some lake after hearing about what was known as "the Magic Worm" that's supposed to gaunt people a wise in hopes of returning back to past, the creature emerged from water as it was revealed to be conjoined in two. The worms tell Jack only one of them and ask him riddles if he were to guess right, Jack would be sent back to past but guessed wrong and will the be digested over 500 years. Jack however, asked them a riddle just as right head eats him whole. It turned out there was never anything magical about the worm as Jack meets several men inside the belly of the worm and soon figured that there is no magic.

It is never seen nor mentioned how Jack got out of the worm afterwards, however, it's more than likely he cut his way out of the worm's belly with his sword, therefore probably killing it.