A small patch of ground on the World 5 map to the south of 5-7 and the Castle can be investigated, revealing a pipe that takes you to a small T-shaped island off the main island. There are two more patches of ground that can be investigated. The southern patch reveals a pipe that teleports you back to World 1. The northern patch takes you to another island where a golden train rides across golden tracks. This is a special bonus level.
There are no collectibles to worry about here, and no enemies on the money train. However, there are a lot of Coins, in piles, and in a gold Shell that you can carry or kick around the train. You won’t be leaving this train without at least a few extra lives. On top of all that, the pipe at the end of the train takes you straight to a Lucky House game, giving you another chance to earn more Coins and lives. You get only one shot at this level before it disappears from the World Map, so make it count!