Key

A key is an item that is used to bypass certain barriers preventing progress beyond them. They can be small enough to be handled by a leader or large enough that they must be handled by Pikmin, and upon collection or use, may unlock doors or special gates or reveal the entrance to the next sublevel, floor, or section of a cave, tower, or dungeon.

=In fanon games=

In Pikmin Adventure (Neini version)
Keys are items scattered all over the worlds in Pikmin Adventure. Resembling smaller versions of from, they allow unlocking locked doors, passing certain gates, and more. Keys are often cleverly hidden to make finding them more difficult.