I believe it is only on the Northern itineraries--the Wonder's Alaska ones, and the Magic's Northern European ones. Since those itineraries don't have a pirate night/fireworks, they have a variety of Frozen activities leading up to the Freezing the night away deck party...Anna's chocolate chase is part of it--they leave the sheet in your room the night before, you have a day to answer the questions and find the picture in that location, leave the paper in your room the next morning and you get a chocolate. (When we did the Alaska trip in 2016, the questions were in the personal navigator and spread over 3 days...our 2018 Magic cruise it was all in 1 day, and I believe the Wonder has switched over to that as well.