From the Super Mario Wiki
If the player decides to stop here, they meet Shy Guy, the train conductor. If the player accepts his quest, Locomotionless, he explains that the train has not run since yesterday because the station has run out of coal, and requests that the player obtain some for him. The player can find coal for him at the Vending Machines, also in the Town area. If the player returns to the Train Station with the coal, Shy Guy rewards him or her with the Gaddget Cake Maker.