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Coin Express, or World 5-Train, is a bonus level, found in World 5 of Super Mario 3D World. This level can be located by finding a Warp Pipe on the map in front of King Ka-thunk's Castle. When the player comes out of that pipe, there will be two Warp Pipes, the top of which leads to the bonus level. This is an auto-scrolling level filled with Coins, Coin Stacks, Coin Rings, and Gold Shells. If the player loses a life in this level or clears the level, they cannot play it again immediately. Instead, they will have to play 25 more levels to be able to play it again.
The level starts on a platform with a train nearby. The player is required to hop on the train in order to grab some Coin Stacks and a nearby Gold Shell, with some Coin Rings in the distance. After some more Coins and Coin Stacks, the player will reach the end of the level. They can choose to go inside a nearby crevice which hides a P Switch, revealing more coins, before hopping into the nearby pipe. This takes them to a slot machine game, which ends the level.