Defeat all of the dungeons. (Be sure you save it after you defeat the last dungeon.) When you defeat the last dungeon, go get Lady, save it, and then go close the book. Wait for all the credits to end, you will see a movie, after the movie it will ask if you want to save it or not, save it, and load your game back up. Go to your monster house, go to encapsulate monster, and there you will find the name "Cooks" Take him out, and he'll be one of your monsters!