Headcanon, fanon, terms and favorites

Ok, lets have some fun today and talk about what canon, head canon and fanon are, and my favorite head canon.

Canon, I think we all know what this is, official facts from the show and official tie in products (books and comics)
Head canon, I think most are familiar with this one, its something a fan, writer or artist comes up with, a fact to fill in holes in the canon
Fanon, now this is a more obscure term. Goldfur uses it, and I have heard others within this and other fandoms use it. Basically its the same thing as head canon, except that this is when said head canon has been accepted by fandom as fact. Like head canon, its not fact, more a patch, but it might as well be true until the canon confirms or contradicts it.

So why bother defining those? I would say why not, but I actually had a minor dust up with someone who swears there's no such thing as fanon, or more to the point, that fans can't fill in the blanks themselves beyond head canon. No, I don't get it either, but whatever.

So, what head canons do I love? Not like, but love? You can thank two stories for these three:

Wind Rider is Scootaloo's father. Dunno who that is? He's the jackass that tried to get Rainbow kicked out of the Wonderbolts in the episode Rarity Investigates. Since I stopped reading it, I can't provide you a link to the story in question, but that was the best thing in the story, and honestly a rather brilliant idea. He got a homeless mare pregnant, and she was wise enough to leave, but when she gave birth, he used his connections to take her newborn while she slept. Said newborn, Scootaloo was abandoned at the Ponyville orphanage, presumably because she was defective. Yeah, this sounds like something I'd expect out of him, don't you?

These next two come from Orpheon'sPerspective.
•Philomena isn't Celestia's pet, she's Sunset Shimmers. Hatching a Phoenix egg was Sunset's test to get into Celestia's school, much like Twilight's was hatching a dragon edge. After she dove into the mirror, Celestia has taken care of Philomena all this time.
•You can grow into becoming an Alicorn, but the reason Celestia disintegrates ponies and takes them to a pocket dimension not unlike the dreamscape is because growing into Alicornhood is not pleasant. Imagine slowly growing a set of wings, having them slowly tear their way out of your body, and you can understand why she does this.

I think those are great ideas, what great ones have you come across?