This one is rather obvious. During the main quest, Guybrush will have to obtain an item from Gullet, one of the LeChuck's crew, in Part III. It's a book of terrible poetry. When back to Mêlée Island in Part IV, just do what Guybrush promise Gullet in order to obtain the book of poetry - which is bring it to Conrad Lee, the curator of the Museum of Pirate Lore / editor of Pirate Times.