Doppio is friendly, honest, and a bit cowardly. He regularly hallucinates random objects as "phones" with which he talks with his alter, Diavolo, not knowing that they share the same body. Doppio mostly behaves like a good-natured person and is by default a friendly and polite individual. Doppio seems to be largely unaware of what the objects he hallucinates as "phones" really are, being an ice cream cone, a burned cigarette or even a frog.