When Pope Formosus died in 896, after a five-year jaunt as pope, he was interred in St. Peter’s Basilica, where all papal corpses end up. Pretty ordinary first burial.
His successor Pope Boniface VI took charge of the Church and things hummed along nicely for 15 days, until he dropped dead too. Then things got a little dicey for Formosus. Because the next pontiff, Stephen VI, had some unresolved beef with the dead Formosus (you can read more about the related papal politics here), so he did what any reasonable spiritual leader would do: he had Formosus exhumed and made his corpse stand trial.
This exercise of justice, since known as the Cadaver Synod, was a showy affair. The papal corpse was decked out in his fanciest ruby clothes, set atop a throne and made to endure a grilling. But wait, how’s the dead man going to answer questions? No problem. Pope Stephen had that covered. A deacon was tasked with speaking on Formosus’ behalf. Here’s a 19th century painting by Jean-Paul Laurens depicting this amazing scene of Catholic justice.

Unsurprisingly, perhaps, Pope Formosus was found guilty at this trial. His papal orders, decrees, etc. were all voided, his fancy clothes were stripped from his corpse, and his body was pitched into a stranger’s grave. Burial number two.
The quiet peace of a grave, however, was presumably too dignified for the disgraced pope. So he was dug up, and tossed into the Tiber River instead. Water burial makes three.
But the Tiber wouldn’t hold Pope Formosus for long. A monk rescued his body, and then I guess just stashed it away somewhere, because after Pope Stephen VI was murdered the following year and Formosus’ reputation was rehabilitated, the wandering corpse got the all-clear to be reinterred at St. Peter’s.
Four burials, only to wind up right back where you started. There’s just no real progress in the Afterlife.