Cappy is a character in the game Super Mario Odyssey who serves as Mario's companion throughout his adventure. Cappy is a sentient hat that possesses the ability to transform into a variety of different objects and creatures when placed on someone's head.

In the game, Mario is on a mission to save Princess Peach from the clutches of Bowser and along the way, he teams up with Cappy, who has a personal vendetta against Bowser as well. Together, they travel across a variety of different kingdoms and use Cappy's unique abilities to navigate obstacles, defeat enemies, and solve puzzles.

Cappy can be thrown by Mario to attack enemies or break obstacles, and can also be used to capture and control other creatures in the game. Additionally, Cappy can provide Mario with special abilities depending on the creature he captures, such as swimming faster or jumping higher.

Overall, Cappy is an integral part of the gameplay in Super Mario Odyssey and is a well-liked character among fans of the game.