From the Super Mario Wiki
“Honestly, a dog could be a better servant!”
In the episode, Princess Toadstool had become increasingly concerned over King Windbag's cold-hearted, bullying attitude and had sent Luigi to sort things out with him. Shortly after arriving at King Windbag's castle, Luigi and King Windbag were attacked by Hip and Hop Koopa, who stole the king's magic scepter and turned him and Luigi into dogs.
King Windbag and Luigi attempted to give chase to Hip and Hop and ended-up chasing them through a Warp Pipe to Miami, Florida. As Luigi was chasing down Hip and Hop through a dinner party, King Windbag was captured by a dog catcher named Herman, who later captured Luigi.
While in the dog-pound, King Windbag is forced by Luigi to cooperate with several dogs to escape the pound. Succeeding in their escape, King Windbag and Luigi manage to track-down Hip and Hop to the Kennedy Space Center, and, after some trouble with Herman, manage to capture the Koopaling twins.
King Windbag manages to reclaim his scepter and returns himself, Luigi, Hip and Hop back to Mushroom World. As a result of his experiences in Florida, Windbag's heart of ice melts, and he vows to "turns over a new leaf" and become a kind king and stop bullying his servants.