Multiple Personality Disorder

Dissociative identity disorder is a psychiatric diagnosis and describes a condition in which a person displays multiple distinct identities or personalities (known as alter egos or alters), each with its own pattern of perceiving and interacting with the environment.

Tuong Lu Kim whose real persona is Dr.Janus suffers from this illness.Butters Stotch  was also diagnosed with this disease,his most prominent persona is Professor Chaos.However Butters is only playing as Professor Chaos.