gives you a set of tasks to complete for rewards each day called Daily Wishes, which is a great way to earn extra Diamonds in addition to claiming them with other currencies through redeeming active codes.
Daily Wishes can ask you to perform a mix of tasks, from collecting some plants to entering one of the Challenge Realms, but one task that can show up might not be as easy to figure out as the others.
That mysterious task is riding the Choo-Choo Train. You might remember your first encounters with the train in during Chapter 5 of the main quests, where you're interacting and working with Pieceys.
During these quests, you see broken parts of a train before you arrive at the functioning train, leading to a sequence where you go through obstacles as you try to reach the engine car before learning that you have to disconnect that car to save the rest of the train.
So, figuring out how to find and ride the train after that sequence might not be very clear. As you might expect, you have to complete the train section of Chapter 5 before you're able to return and take joyrides on the train.