You know, I've seen Harry as the Hulk before (Neville had an acciend in Potions with a rage-reducing concoction, you've probably read it) but the Hulk, aside from being created by potion reagents as opposed to gamma radiation, was otherwise entirely unmagical.
Now that I've had some time to ponder that, I realize how completely bonkers that is. The Hulk was Bruce Banner's anger made manifest. What do people, men predominantly, do when they're angry? They hit stuff. What does a Harry do when he gets angry? Ask his Aunt Marge, before she was obliviated, at least.
Magic plays a part, I'm sure of it. I'm just curious as to how.