Pinocchio
Pinocchio is a character from the Disney film of the same name and was a featured character in Kingdom Hearts.
Story
Pinocchio was, originally, a wooden puppet brought to life by the Blue Fairy after his maker Geppeto wished for a son. Jiminy Cricket was assigned to be Pincchio's conscience. Unfortunately for all three, the heartless came and destroyed their world, causing them to become separated.
Jiminy ended up at Disney Castle, where he became the Royal Scholar and was eventually assigned to travel with Donald and Goofy (and later Sora).
It is unknown where Gepetto went, but as Sora, Donald and Goofy travel throughout the different worlds, they discover Pinocchio running around Traverse Town. Without his conscience, Pinocchio has been misbehaving, but in the end Jiminy manages to set him straight.
Pinocchio promised Jiminy that he would behave from that point onwards and find his father.
Inside Monstro
Some time after Pinocchio escaped Traverse Town (currently unknown how), he was reunited with his father and both of them ended up inside of Monstro.
When Sora, Donald and Goofy are on their way to Atlantica or Halloween Town (depending on the player's choice), Monstro comes and swallows their Gummi Ship whole. The trio wake up inside of Monstro's mouth and, after exploring, reunite with Pinocchio once more and finally meet his father Gepetto.
Pinocchio was a mischievous boy and wanted to play a game. He ran away from Sora, Donald and Goofy into Monstro's bowels, hoping to play a game of catch, but instead he got kidnapped by Riku (it's unknown how Riku got to Monstro). Riku leads Sora, Donald and Goofy on a merry chase of hide and seek, constantly throwing taunts to his old friend.
However, the boss for Monstro Parasite Cage attempted to steal the puppet's heart off of Riku. It was because of this that Riku and Sora teamed up to destroy it - but after rescuing Pinocchio Riku kidnapped him again and eventually took Pinocchio's heart, believing it would replace Kairi's.
Thanks to the compassion of Jiminy Cricket and Pinocchio's friends, together they managed to return Pinocchio to his former self. After Sora, Donald and Goofy leave Monstro, it is later seen that Pinocchio and his father live in Traverse Town, trying to piece their life together again.
At the end of the game, during the credits, Pinocchio had become a 'real human boy'.