Doopliss is a Duplighost that lives in the Creepy Steeple of Twilight Town in Paper Mario: The Thousand-Year Door. He appears as an enemy of Mario several times throughout the game, and is the boss of Chapter 4. He causes the members of Twilight Town to become pigs whenever the bell tolls, and attempts to steal Mario's identity. He has the special ability of stealing another character's body when copying them, something that most Duplighosts are unable to do. He later becomes a member of the Shadow Sirens, replacing Vivian.
Doopliss is, in his regular appearance, a Duplighost who wears a blue bow tie and a blue cone-shaped hat with red stars on it. His eyes and mouth appear bigger than those of the Duplighosts in Paper Mario, his sheet is whiter, and his feet are orange instead of gray. Doopliss is, as a Duplighost, most likely undead. He is referred to as a demon by the inhabitants of Twilight Town.