One of the lousiest arguments against the Papacy and Roman Catholicism is that there was a “Pope Joan,” a female pope. Fortunately, this myth seems to be dead, though I did recently hear the comment in passing by a fellow Latter-day Saint (I managed to correct them on this myth of history). While I do not believe that the bible and history supports the dogmatic theology of the papacy one finds in Catholicism (esp. as defined at Vatican I), one should make sure one uses the best arguments against the best arguments, not, well, utter nonsense.
Catholic apologist Patrick Madrid has written a bit on this issue, including a whole chapter in his book, Pope Fiction. Here is an online article refuting this claim: