In one game as Egypt, I had Abysmal relations with everyone, despicable reputation, was at war with several christian factions, and even called a Jihad down on Rome. The Papal States still asked to be my ally. I thought it would be funny so I agreed to the alliance. Big mistake. A few turns later, the Pope called a crusade against my capitol at Constantinople, and 8 different christian factions declare war on me. The Papal States were still allied to me though. The pope also seemed to time his crusade to coincide with a Mongol invasion of my lands That was one wacked out pope.

Check it out:
https://forums.totalwar.org/vb/showthread.php?t=76406