It actually isn't the mythology so much -- I accept that they're going to bastardize mythology on SG (I have to, because I've studied most of the major mythologies of the world at some point or other). It's things like Daniel's "this is based on an ancient Celtic writing system" (WTF?). Costuming and sets that are supposed to represent somebody's romantic vision of the ancient British Isles. Anything, ever, about Druids, especially the faux-mystical stuff. And OMG Druids building Stonehenge, GAH. The Noble Savage in general. SG's Arthurian BS, OMG. AND. THE MISTS OF AVALON IS NOT A PRIMARY SOURCE, PEOPLE.

Er, yeah. I get a little worked up about this. Sorry.

Oh, and piano (or any musical instrument) bugs me, too. I don't even play piano, but I know enough about music to call bullshit on the shoulder thing especially.

I'm blanking on the name of the author of my favorite (respectable) book on Celtic Mythology, which is freaking ridiculous since I had to know the full citation to the letter for my MA exams, but when it comes to me I'll let you know.