There is no Pope John XX. In numbering its pontiffs, the church skipped directly from Pope John XIX to Pope John XXI because confusion in the records led Pope John XX to believe that Pope John XIV had been succeeded by a second Pope John XIV, but that Pope John XV to Pope John XIX had overlooked his existence. So Pope John XX ordered his designation changed to Pope John XXI so that Pope John XV to Pope John XIX could be renumbered Pope John XVI to Pope John XX. But there was no second Pope John XIV, so Pope John XV to Pope John XIX were correctly numbered and the new Pope John XXI should have remained Pope John XX.

Worse, Pope John XVI was a disputed claimant whose number should have been reused, moving all subsequent Popes John back a notch. That hasn’t happened either.

The bottom line is that there’s still time for you to be Pope John XX if you want to. You just need to be elected by the College of Cardinals.