There's the whole historical inconvenience that Michelangelo labelled his sketches that he prepared for his Last Supper. Yes, John is John, and The DaVinci Code is a spiralling work of fiction based on faery dust.
This sort of thing normally wouldn't bother me if it weren't for all the other garbage accusations being brought against the Catholic Church as of, oh, how many decades has it been?
My other favorite work of Catholic historical distortion? The cover of Hitler's Pope that depicted Pope Pius XII being saluted by a German soldier. The problem, of course, is that this was not a Nazi soldier (despite the way this fraudulent photo has been touched up to bring about the resemblance of one) Indeed, Hitler hadn't even begun his rise to power and Pius XII wasn't even Pius XII, but Bishop Pacelli, who would become Pope 11-years later. But, my, was it dramatic!
Did I just write Michelangelo? Geez, time for bed. ;)
Davinci Code? Hello? That would be Leonardo. ;)
Same difference at this hour.