Bowser and the Broodals, a family of anthropomorphic rabbits serving as his wedding planners, kidnap Princess Peach from the Mushroom Kingdom and take her aboard Bowser's airship, intent on forcibly marrying her. Mario attempts to rescue her but is thrown off the ship by Bowser's hat and falls into the neighboring Cap Kingdom. With Mario gone, Bowser stomps on Mario's cap and lets it drift into the ship's rear propellers, shredding it to pieces.
A piece of the hat is grabbed by Cappy, one of the Cap Kingdom's sentient hat-like creatures called Bonneters; he explains to Mario that Bowser also kidnapped his sister Tiara to be used as Peach's wedding tiara. Cappy joins Mario and takes the shape of Mario's cap, providing him with the ability to throw his cap and temporarily capture other creatures and objects and utilize their abilities. They travel to the nearby Cascade Kingdom, recover an airship called the Odyssey, and begin pursuing Bowser.
