Red Key

The Red Key is an item found in several Mario RPGs.

In the original Paper Mario, the Red Key unlocks the red door in the Crystal Palace. The Red Key is to the south of the entrance room. Mario must first go to the north side and break a wodden floor with a Tornado Jump. After doing this, where a red cross appears on the floor in the south side will become a hole. The Red Key is in a chest at the end of the road down this hole. The in-game description reads, "A big red key."

In Paper Mario: The Thousand-Year Door, another Red Key unlocks the cage the Puni Elder was imprisoned in during Lord Crump's invasion of the Great Tree. It is held by an X-Naut in the storage room just west of the prison. After Mario enters the storage room, the X-Naut becomes conscious, mistakes Mario for hitting him, and gets in battle. Defeated, the X-Naut drops this key.

In Mario & Luigi: Bowser's Inside Story, a red key can be found on the second floor in Peach's Castle. It is carried by a Fawfulcopter which Bowser chases after. When Bowser chases it to the highest spot on the cliff using the Spike Ball ability, the Fawfulcopter has nowhere to go and Bowser can hit it for the key. With the red key, Bowser will be able to open the red door he encountered eariler and save his Magikoopa minions, thereby getting the Magikoopa Mob attack.