On a random map, a hero not associated with Necropolis can only learn Sorcery through a scholar. :)
There's a bug where if you have 2 identical heroes in a castle – one visiting, the other guarding – and if the cloned hero has a Legion torso, the creatures become level 4 + 3*2 = 6. :)
The biggest bug, in my opinion, is that for 1000 to 54000 gold, you can create a simple scroll with a spell. :) Whoever knows this bug will be the champion among all of you. :) I found it by accident. :) It was fixed only in version 3.58, I think.