The King of the Koopas has been captured. His children are alone and on the run, their strength not enough to stop the enemy. Their only option is to ask for help from their greatest foe; if they can survive the journey across the Eight Lands.
Bowser's good at knowing when Junior's upset, and, like any good parent would, he tries to cheer him up. Turns out, what Junior's unhappy about is something Bowser can't quite seem to get.
When a kidnapping mission turns into a crash-landing, Bowser makes an important promise to Peach. After a few incidents, of course.
Junior says something that Peach doesn't approve of, and she goes to confront the one who taught it to him; his father.