Key Mini Mario

Key Mini Mario is a type of Mini Mario with a key, which appears in several games in the Mario vs. Donkey Kong series.

Mario vs. Donkey Kong
Key Mini Mario first appears in Mario vs. Donkey Kong. It appears in each level of the game's Plus worlds aside from boss levels, and is introduced in Level 1-1+ of Mario Toy Factory. Instead of carrying a key by himself, Mario must lead a Mini-Mario with a key to the locked door in each Plus level. The Mini-Mario in each Plus level sits idly until Mario approaches it, after which the Mini-Mario follows Mario. If Mario and the Mini-Mario reach the locked door, the Mini-Mario unlocks the door and both Mario and the Mini-Mario enter the door, completing the level.

Mario vs. Donkey Kong: Minis March Again!
Key Mini Mario reappears in Mario vs. Donkey Kong: Minis March Again!, being introduced in Room 1-Key and appearing in subsequent Key levels. Key Mini Mario appears in levels with a locked door, which must be unlocked by a Key Mini Mario in order for any Minis to enter the door.

Mario vs. Donkey Kong: Mini-Land Mayhem!
Key Mini Mario reappears in Mario vs. Donkey Kong: Mini-Land Mayhem!, where it appears in the eighth course of each attraction, along with a locked Exit Door. It functions identically to its appearance in the previous game.

Mario and Donkey Kong: Minis on the Move
Key Mini Mario reappears in Mario and Donkey Kong: Minis on the Move in levels with a locked goal. Minis other than Mini Mario can also use keys in this game. In Mario's Main Event, a Mini does not have a key at the beginning of a level with a locked goal; instead, it must collect the key within the level, then use it to unlock and enter the goal. In Many Mini Mayhem, one of the Minis in a level with a locked goal spawns with a key; this Mini must reach the goal first in order to unlock it.

Mario vs. Donkey Kong: Tipping Stars
Key Mini Mario reappears in Mario vs. Donkey Kong: Tipping Stars, with the same function as in Mario vs. Donkey Kong: Minis March Again! and Mario vs. Donkey Kong: Mini-Land Mayhem!.