From "Treehouse of Horror" to "Treehouse of Horror XIII", all three segments were written by different writers. In some cases there was a fourth writer that wrote the opening and wraparound segments. For "Treehouse of Horror", there were even three different directors for the episode. However, starting with season fifteen's "Treehouse of Horror XIV", only one writer was credited as having written a "Treehouse of Horror" episode, and the trend has continued since.