The Letter "p"
The letter p is a special item in the game Paper Mario: The Thousand-Year Door.
Mario and Vivian needed the letter p to guess Doopliss's name, because while guessing his name, their letter options lack this letter. This is also a way to deter players to not skip through the chapter. Although a capital "P" is always available when Doopliss prompts Mario and Vivian to guess his name, using it does not work; the spelling is case sensitive.
To find the letter, Mario must use Vivian to access a secret portion under the well in Creepy Steeple, using her Veil ability. 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
- Doopliss is called "Rumpel" (ランペル Ranperu) in Japan. The missing letter in the Japanese version is ン ("n" in the katakana syllabary) rather than the English "p". In other languages, where Doopliss is called "Rumpel" or "Rampel", the p is also the missing letter.
