Roleplaying as a pre-established character, in my opinion, is one of the largest tasks ever. Roleplaying as your own creation? Not terribly hard. Roleplaying an interpretation? Still not too bad. But, to take up the mantle of any pre-exsting character from any canon is not only difficult, but it's a task that's risky for the professionals in the field - Americana comic writers. Look at Batman, for example. A story and character retold a thousand times, sometimes completely varying from some of the original concepts. Yet, some iterations are considered brilliant while others are bastards. Fact is, you're judged on what you keep true and what you change, and not all opinions are universal. But, when characters dictate more of a roleplay than either its setting or plot, which in many casual and free roleplays is the case, how you actually act out that character means a whole lot.