@Olivier5,
No it's not. A lot of people actually believe Sherlock Holmes exists/existed. 212b Baker Street regularly receives letters asking Sherlock to investigate Watergate 9/11 amongst other things.
This letter is quite good, (I know your(sic) six feet under) .
Given that we live in an age with information ready at the click of a button, yet people still believe he existed, it's totally conceivable that, in an age where technology didn't exist, people could believed a fictional character existed.