Someone who basically is posing as something he/she isn't. A fan who wishes they could be their idol, usually a super hero type, leader, musician, actor, or porn star.
A desire to copy someone else, to dress or talk like the person they are trying to imitate.
The attempt to create their own personality, based on another, by mimicking their mannerisms.
Can include changes in behaviour and attitudes, in how they interact with others, and not just limited to dress, or speech.