Cumania invading Germany.
HRE getting Norway and England in 1066.
My Mande character being complemented for my fair skin and blonde hair...
Caliphate declaring claim wars on me when I'm 50 times his size (my local cataphract retinue could squish him)
Abbasids gaining a county in Sweden
Abbasids controlling all of Syria, Jerusalem, Persia, Mesopotamia, Arabia, Egypt, Armenia, Georgia, Anatolia, Greece, Serbia, Hungary, Bulgaria, and Wallachia. It was terrifying.
An AI Britannia with all of de jure, plus Northern half of Spain, plus Scandinivia, plus Lithuania, plus Rus, plus Frisia. What a monster that was to put down.
Oh, and oddest of all, a zoroastrian amalfi.