Monstro

Monstro is both a character and world from Kingdom Hearts. Like many of the worlds from the original game, it also appears in Kingdom Hearts: Chain of Memories as well.

Though technically an interspace creature, an unbelievably large blue whale with man-eating tendencies, to be exact, it acts as a world in the first two Kingdom Hearts games, due to its massive size. Pinocchio's World, as of yet unnamed in the Kingdom Hearts universe, was destroyed by the Heartless. Monstro is also one of the only three Disney-based worlds in Kingdom Hearts that does not have you fight alongside a protagonist of the original movie it is based off of; the other two are Wonderland and Olympus Coliseum.

It is possible to defeat the game without "locking" Monstro by skipping the final boss fight, but Gepetto and Pinocchio will not appear in Traverse Town and the game's secret ending movie will not be unlocked.

Monstro is the ruler of this world, as well as the world itself.

Setting
Monstro is so enormous that its playable map is bigger than that of some other worlds, like Wonderland. If one leaves Monstro and tries to go to the different direction, then they will be caught by Monstro again and Monstro will appear twice on the map. Sometimes, attempting to return to Monstro will not work, as Monstro will temporarily leave his spot; Goofy will express his relief at this and the party will have to come back later. Monstro has one of the most confusing layouts of any world; it essentially an interconnecting maze. It takes a lot of patience and a little ingenuity to make your way all the way through. Many openings open into different parts of the same room, allowing for much confusion of anyone trying to work their way through. As the surfaces in each area look the same, the only visual differences in the Chambers are the ledges, the treasures, and the occasional barrels and debris found in them. In addition, the Chambers are marked only with numbers and are not traveled through in numerical order. Finally, Monstro defies anatomy as it is known, so natural assumptions such as going "down" to reach his stomach, for example, do not hold (you have to climb up his throat.)

Sora and his party enter through Monstro's Mouth, the largest room in the world. Here, among the piles of wood and shipwrecks, the party will come across Gepetto and Pinocchio, as well as the world's Save Point. Troublesome Pinocchio leads the party down the into the whale's innards. Chamber 1 is the arrival point for the party here. The lowest door leads to a dead-end at Chamber 3, marked by a large piece of debris blocking off the other lowest exit. The door on the ledge of Chamber 1 will take the party to Chamber 2, which leads to Chamber 3 going down, and to Chamber 5 going up. Chamber 6, which comes soon after, stands out because it is formed like a set of stairs. Chamber 5 will also send the party to Chamber 4, from which the Bowels and first battle with Parasite Cage can be found, as well as a Save Point.

Returning to the Mouth and using High Jump, given by Gepetto, the party can at last reach the Throat, a tall, pink chamber with a series of ledges to ascend. At the top, the party can reach the Stomach and the final boss battle.

In Chain of Memories, there are extensions coming out of the floor which can be hit or jumped on to gain items.

Kingdom Hearts
Sora, Donald, and Goofy are flying away from Agrabah to get to their next destination; they spot something huge flying towards them on the Gummi Route. They quickly realize it is a massive whale, but cannot get out of the way before the beast swallows their ship whole.

Inside Monstro's flooded mouth, the trio finds Pinocchio again and meets his father Geppetto in a broken ship. While speaking with Geppetto, Pinocchio slips off to explore Monstro. Sora and his party quickly run after the puppet into the bowels of Monstro. There, he finds Riku; the two friends exchange some quick words before Riku runs off with Pinocchio, hinting at Riku's newfound darker nature.

Sora, Donald, and Goofy chase the two through the whale, until he eventually finds them in a large circular chamber that are the bowels of the beast. Pinocchio is taken captive inside the Parasite Cage Heartless. Sora and Riku team up to take down the Heartless, but are unable to completely destroy it. Riku takes Pinocchio; his words hint to Sora that there is something different about his old friend. Sora tracks the puppet to the Stomach, where Riku and the Heartless attempt to take Pinocchio's heart, but fail. Riku flees as Sora enters the belly of the beast where he defeats the Parasite Cage once and for all and rescues Pinocchio.

From all the commotion in his organs, Monstro spews out the Gummi ship and the trio to prevent any more trouble. Pinocchio and Geppetto also escape and set up a shop in Traverse Town.

Kingdom Hearts: Chain of Memories
In Chain of Memories, Riku's part in Monstro is taken out. But the chase for Pinocchio is the same and his reunion with Jiminy. The fight with the Parasite Cage stays the same except that you do not fight it twice. The last story door actually is a fight with Heartless to make Monstro spit out Pinocchio and Geppetto.

Dalmatians

 * 55, 56, & 57 - Chamber 3 on one of the mid-level ledges.
 * 73, 74, & 75 - Mouth, on the tall pile of wreakage next to Gepetto's ship.
 * 76, 77, & 78 - Chamber 3 on the highest ledge in the room.
 * 79, 80, & 81 - Chamber 5, on the high ledge.

Trivia

 * If you exit the world after the initial cutscene and come back after the the events of Hollow Bastion, Riku will still somehow be there despite being taken over by Ansem