i think you have the cart before the horse - no one comes into acting as a celebrity - there are maybe a tiny handful who start as pre-teen disney stars, but most have 'earned their stripes' working in anonymity then got a lucky break somewhere along the way
it's the industry that creates the ego maniac - publicists hype their shows and the public gloms onto to someone and then the publicists create celebrity from that
same with pro athletes, same with music stars, et al