Board Thread:Questions and Answers/@comment-26043322-20150201171940/@comment-24577221-20150201173056

The "likes" shown for each monster in the game include one mystery item, represented by the question mark. It's a specific item, known by the game's creators. Game players can spend time figuring out what that item is, moving things around, buying decorations, and watching for the monster's Happiness to change... or, since you've found this wiki, you can "cheat" and look up a monster here and see what it likes.