Mario Key

The Mario Key is an item in Super Mario 64 DS. It is the key that unlocks the door that Mario is trapped behind and the only character key required to beat the game. The Mario Key was used by Goomboss to trap Mario behind a door in the Mushroom Castle after he captured him. It is obtained by Yoshi after he collects eight Power Stars, enters the room behind Princess Peach's Rec Room, and defeats Goomboss inside the Mario portrait.

The key is about the size of Mario, is made of gold with a large M in the center of it, and has Mario's cap on top of it, though the cap disappears upon the player collecting it. Once Yoshi retrieves this key and brings it to the door Mario is behind, Mario will be freed, and Mario Caps will appear in courses if the player is someone other than Mario.