It's been a long while since Bowser Junior had his amazing adventure. This time he was at his home in the Koopa Kingdom, being in his own castle that he themed after himself, polishing his Junior Clown Car when he heard a train whistle in the distance. Bowser Jr. took a look outside his castle tower, to see a speeding gray Bullet Train go by, with various different enemies on top of it.
Smirking, Bowser Jr. took this as a way to have a new adventure, with it being quite a while to justify this. Putting the last touches on his clown kar, Bowser Jr. jumped into the machine and blasted out of the tower through the window, activating his vehicle's cart mode as orange wheels popped out from the bottom, dashing afterwards.
A train conducting Whomp with blue clothing was driving the bullet train towards the northern direction as he looked out the window, to see Bowser Jr. swiftly approaching the train. He shook his stone head, contacting the other enemies on the train to go and get Bowser Jr. away from the train. Willing to do something, the enemies all headed to the back of the train, standing on the last train car as they waited for Bowser Jr. to get close, preparing for their onslaught.