The persona is a mask, a shield, and a character. Out of insecurity or entertainment, the persona is used to channel the ego of his/her character—so the character’s ego would be affected instead of their own. Most people carry a shell, to some degree or another.
Of the entertainment factor, stand-up comedians act differently on stage than in real life. Take Albert Einstein and the late Phyllis Diller, for example. At home, they never wore their signature hair, and Diller never held her signature cigarette holder. (And, yes, I know Einstein wasn’t a stand-up comedian.)
Then, there’s the specific act of self-deprecation, used to keep oneself from becoming too large, and to quash that higher-than-thou impression. Being opinionated is one thing, but having an ego the size of Mount Rushmore is another. There’s something to be said about not allowing yourself to be idolized, to instead promote an ideal or set of ideals. That is the nature of the role model. It is not necessarily you, but the image put out there to inspire values.
Maintenance of that role model is yet another thing, one most difficult for a narcissist.
Narcissism (n.): the instance of being over-self-congratulatory, such as putting up paintings or photos of yourself doing mundane things as if they’re major accomplishments—all over the place.