irrational belief that one is another person
Appersonification ... A delusion in which one assumes the character of another person. ... (05 Mar 2000) ... 
(ә-pur″so-na´shәn) appersonification.
Type: Term Pronunciation: ă-per′sŏ-nā′shŭn, ap-er-son′i-fi-kā′shŭn Definitions: 1. A delusion in which one assumes the character of another person.
the unconscious assumption of the personality characteristics of another, usually well known, person.