Doopliss

“I'm busy thinking of new pranks and stuff! It's not easy either! Now get lost! ..Of course you guys WON'T. No way you ninnies go away quietly, am I right?”

—Doopliss, Paper Mario: The Thousand-Year Door

Doopliss is a Duplighost who caused trouble at Twilight Town, turning everyone into pigs and stealing Mario's identity and teammates, leaving Mario nothing but his shadow. His base of operations is Creepy Steeple. To find out what his name was, the player had to find the Superbombomb and give it to the Shadow Siren Vivian. Vivian joined Mario and the two had to guess Doopliss' name, because as long as his name wasn't known Doopliss could continue to use his most powerful magic. The only thing Mario and Vivian were missing was the lower-case letter P, which Doopliss had hoarded in Creep Steeple's basement in protection of Doopliss's Parrot. After getting the letter P, they correctly guess Doopliss' name and Doopliss flees back to Creepy Steeple. While battling Doopliss, Vivian discovers she joined Mario (since he was a shadow, she was not aware she was joining the very guy she was ordered to defeat) and she takes a little time to think it over. Vivian decides to join the party for real, because Mario treated her a lot nicer than Beldam and Marilyn ever did. Upon defeat, Doopliss is unmasked, surrenders Mario's identity and teammates back to Mario and gives Mario the Crystal Star he deserves. He flees Creepy Steeple in humiliation and joins the Shadow Sirens later on. During his time with the Shadow Sirens, Beldam insists on calling him a 'freak in a sheet'. He becomes a lot nicer at the end of the game and pursues a career in acting alongside Flurrie. His only appearance is in Paper Mario: The Thousand-Year Door.

Trivia

• Doopliss' name probably derives from a combination of Doofuss and Duplicate, or a play on the word Doop (slang term for tricking a person). It may also come from Duplighost, the name of his species.
• Doopliss' Japanese name is Ranperu, which translates to Rumpel, which is the Doopliss name in the Spanish version of the game, and comes from the fairy tale character Rumpelstiltskin, as both offer the same challenge: to have another guess his name.