Thinking of Harry Potter always makes me want to get Improved Familar feat so I can get a hippogriff. But then I think about how many more alter self spells I'd need to get it around Underdark b/c of the large size. And my sister always tells me how Hagrid has awesome spell resistance, and so do titans in D&D, so then I always think about that for my Half-giant too. Well my PrC eventually gives SR, so I will eventually have that part covered. Not that I was totally going for Hagrid, my guy is a lot more into carnage... but how many half-giant wizards do you run into, even if you're in the business? So obviously I get a lot of ideas for my PC from him.
I haven't read any of the books yet, but my sister tells me about them all the time and some of the stuff drives me nuts. Hagrid should have just busted skulls on those death eaters, the centar divination teacher should have warned Dumbledore/Harry/OotP/etc, Ron/etc should have stoped Draco before they got to Dumabledore (plus the toughest wizard in the world shouldn't be taken down by a dork like Snape, let alone be threatened by some pimple-faced teenage punk). The good guys are way tougher, yet the bad dudes win, it makes no sense.
About Dumbledore knowing a lot, can't he see through all those trading cards of himself or something? Seems like he could use a lot of divination magic with them, but it would mostly be current events stuff, not old stuff that happened forever ago like Voldemort's horcruxes.
The scar thing is obvious, they talk about that in even the first and second movie. The scar always goes weird around Voldemort and Harry has some of his powers and such. The horcrux just explains more about it.
I could always be wrong though, I've only saw the movies.
