There was never a Pope Joan. If it was the Maid of Orleans...

I think Sug was referring to the fictitious tale of a "Pope Joan", which was a plagiarism of a Roman legend having nothing to do with the Church in much the same way that "The Protocols of...Zion" was a plagiarism of a French satire having nothing to do with Jews.

Unfortunately, some people still believe one or both of these are true. I think Sug was just joking though.