From the Super Mario Wiki
(Redirected from Final Showdown)
Guard Doors are huge stone faces of Bowser that act as gates in Paper Mario. In three areas of Bowser's Castle a Guard Door can be found, they'll need to have something be done before they let Mario pass. If Mario completes the objective the gate will split in half and open.
The first one Mario encounters opens a trap door, sending Mario to a jail cell. After Mario escapes, the gate lets him in. The second quizes Mario five times on various enemies; however, if Mario answers three questions wrong he is forced to fight three Anti Guys. The third and final Door sends Mario into a battle with the Super Ultra Mighty Koopa Bros. the Great, but they are knocked away by the improved Jr. Troopa, whom Mario then has to fight. The third Guard Door is the exit from Bowser's Castle, leading to Princess Peach's Castle.