Key

Keys are items used for various purposes that appear in many games of the Mario, Yoshi, Wario series and the Legend of Zelda series and related media. Though their appearance and usage varies, they are typically used to open a locked door or a secret path.

Super Mario Bros. 2
Super Mario Bros. 2 is the first Mario game to feature Keys and locked Doors. All keys in this game are guarded by Phantos, one of which will chase the player until the key is dropped or used to unlock a door. Unlike many other items in the game, Keys are always visible without having to be rooted up like a Vegetable.

Most keys are out in the open, but at least one was guarded by a Birdo in World 7-2.

Super Mario World
In Super Mario World, Keys and Keyholes can be found in various levels. Bringing a Key to a Keyhole activates the respective level's secret exit. Like other items in the game, Keys can be carried around and dropped or kicked upwards, but they will have no effect on a Keyhole unless held by the player. Yoshi can carry a key in his mouth, but will swallow it if it remains in his mouth for too long. The location of a Key does not reset when it is scrolled off the screen.

Super Mario 64/Super Mario 64 DS
Keys appear in Super Mario 64 and its remake, Super Mario 64 DS. There are only two keys in the game and they can found in two Bowser's levels: Bowser in the Dark World and Bowser in the Fire Sea. Mario gets them when Bowser is defeated. The keys can open Doors of the Princess Peach's Castle. The first key opens the door of the castle's basement and the second key opens the door of the castle's upper floors. If a player attempts to open the door to the upper floors with the basement key, a message will appear to let the player know that that key doesn't fit the lock. Also, a beta key appears in Big Boo's Haunt level.

In Super Mario 64 DS, keys retain their purpose from the previous game, but there are more other kinds of keys. First, there are those that [Rabbit]s steal. The first key Yoshi has to obtain unlocks Princess Peach's Castle; only after he catches that first rabbit can he get inside. There are many other rabbits that can be found in the game, but they only unlock minigames. The second kind of keys the player must collect are held by three bosses (Goomboss, King Boo and Chief Chilly), and are used to free Mario, Luigi and Wario.

Super Mario Galaxy
In Super Mario Galaxy, keys can be collected to automatically open locked doors or force-fields. They are found in galaxies such as the Gateway Galaxy and the Ghostly Galaxy. In the Gateway Galaxy and Ghostly Galaxy, a Grand Goomba and a Boo, respectively, each hold a key which is released after Mario or Luigi defeats the enemies.

New Super Mario Bros. series
In ''[http://mario.wikia.com/wiki/New_Super_Mario_Bros. New Super Mario Bros.]'', at the end of each World from 2 to 7, [http://mario.wikia.com/wiki/Bowser_Jr. Bowser Jr.] places a random boss and if the player wins, a Key will be granted. In New Super Mario Bros. Wii and New Super Mario Bros. 2, when Mario defeats any of the Koopalings at their castles, he'll receive a key that he must grab to exit the castle. This item doesn't serve any other purpose in both games though. In New Super Mario Bros. 3, when Mario defeats any of the False Bowsers at their castles, he'll receive a key that he must grab to unlock the Airship level.