From WiKirby, your independent source of Kirby knowledge.
Waddle Dee Train is a hazard enemy that debuted in Kirby: Triple Deluxe, first encountered in the Old Odyssey level. It can only be defeated with the Hypernova ability.
Waddle Dee Train is unique in that it is an enemy that can be defeated, but at the same time, acts more as a stage hazard than anything else. It does not actively try to hit Kirby or do anything other than roll forward periodically along its track. If Kirby is hit by a Waddle Dee Train, he will splat against the screen and lose his Copy Ability. Waddle Dee Train can be easily inhaled with Hypernova, but it is possible to inhale only sections of the train. Often, Waddle Dee Trains carry chests that can be acquired once they are inhaled.
In Kirby Fighters Deluxe, a Waddle Dee Train appears in the stage Waddle Dee Train Tracks. Before going on screen, a sign will appear to warn the players that it's coming. If the sign is ignored, any Kirbys still on the ground will be ran over by the train. It can appear both from the background and from the right of the stage.
Kirby inhaling a portion of the Train.