I mean...women have had Pope children before. Who knows if they were lesbians or not. I don't think any Anti-Pope ever took over Rome though. I know the HRE had a few during its time, but I don't think they ever won their battles to install their man as the true Pope.
I think you are correct. The Muslims never breached the Vatican, neither did the protestants to actually install power. Some shitty Popes were there, but their religion has had entire reigning power.
I meant before the Protestant Reformation and from the HRE specifically, since those were the only Anti-Popes I knew of, but it seems much more fuzzy than that. The HRE was formed from a priest basically elevated to Pope who then crowned his liege Holy Roman Emperor.
[Pope Clement II] In 1040, he became Bishop of Bamberg. In 1046, he accompanied King Henry III on his campaign to Italy and in December, participated in the Council of Sutri, which deposed former Popes Benedict IX and Sylvester III and persuaded Pope Gregory VI to resign. King Henry nominated Suidger for the papacy and the council elected him. Suidger took the name Clement II. Immediately after his election, King Henry and the new Pope moved to Rome, where Clement crowned Henry III as Holy Roman Emperor.
1378 to 1417 which Catholic scholars refer to as the "Western Schism" or, "the great controversy of the antipopes" (also called "the second great schism" by some secular and Protestant historians), there was a period of great difficulty.
The French cardinals withdrew to a conclave of their own, where they elected one of their number, Robert of Geneva. He took the name Clement VII. By 1379, he was back in the palace of popes in Avignon, while Urban VI remained in Rome.
For nearly forty years the Church had two papal curias and two sets of cardinals, each electing a new pope for Rome or Avignon when death created a vacancy. Each pope lobbied for support among kings and princes who played them off against each other, changing allegiance when according to political advantage.
In 1409, a council was convened at Pisa to resolve the issue. The council declared both existing popes to be schismatic (Gregory XII from Rome, Benedict XIII from Avignon) and appointed a new one, Alexander V. But the existing popes had not been persuaded to resign, so the church had three popes.
Definitely way more complex than one thinks with only a passing glance at their history. :p
EDIT: Was slightly misleading how I had it organized.
I wish this was real life and not a game