The letter "p"



In the game Paper Mario: The Thousand-Year Door, the Letter "p" is an item Mario and Vivian used to guess Doopliss's name, because while guessing his name, Mario and Vivian's letter options lacked this letter. This was also a very clever way to prevent people from cheating (by looking up Doopliss's name on sources such as player's guides and the internet).

To find the letter, Mario is forced to use Vivian to access a secret portion under the well in Creepy Steeple, using her Veil power. There, Mario can roll up into a tube and access a treasure room, where one of the chests contains the letter. By using Veil again, a parrot in the room reveals Doopliss's name for the player.

Trivia

 * Being a letter of the English alphabet, the actual letter "p" has made quite a few appearances in Mario series games, debuting alongside Mario himself in Donkey Kong, which featured the phrases "Pauline" (which was never actually spoken in-game, but mentioned many times in American promotional material), Top, Player, Japan, and "HELP!".
 * Doopliss is called "Ranperu" in Japan. The missing letter in the Japanese version is "n" (though in the katakana alphabet) rather than the American "p".