First theory. Explains everything. Why does the author keep noting that Jon Snow has a "Stark look"? To make sure we don't question whether Ned is his father.

But ah... he could have a Stark look from his mother, Lyanna. Making him the bastard son of Rhaegon and Lyanna, and hence an heir to the Targaryen throne.

Now, the books were always very vague about how exactly Rheagon "stole" Lyanna away. What if he didn't steal her? What if she just loved him? And then, at the end of Robert's Rebellion, she gives birth. The heir is spirited away to the Tower of Joy, where three kingsguard, including Arthur Dayne, protect him (and Lyanna).

The books keep referring to that fight -- and never say what the fight was about.

The books keep referring to a promise Lyanna made Eddard vow to keep -- but never say what that promise was.

The promise was simply to make sure her son, by Rhaegon, was hidden away, and unharmed.

This explains why Ned had a very out-of-character affair. He didn't. It explains why he won't talk about Jon Snow's mother.

Lyanna died in a "bed of blood." Was she stabbed? They never say. Maybe she had just given difficult birth. Because who there would kill her? Her kingsguard was there to protect her; Ned and his allies wanted her alive.

The books also established that Ned would do anything to protect the children of his enemies from harm (he warns Cersie to get out of King's Landing, with her children, even though that warning exposes himself and his family to great risk).

Oh, and why are the Reed children suddenly so important in the story? Why is Howland Reed such a good friend to Ned Stark, so devoted to him? Because only Howland Reed knows Ned's secret. Only Ned and Howland survived the fight with the Kingsguard, and only Howland knows the promise Lyanna made Ned swear.

Now, at first, I didn't love this, because the books already had a swapped-baby-type story: Aegon Targaryen. Aegon Targaryen is supposedly Raeghon's and Ellia's son, rescued by Varys, by swapping him for a commoner's child.

It doesn't seem to me that a book can have two Targaryen changelings in it. One Targaryen changeling too many. It's silly.

So Ageon must be a fake, a pretender.

I think this makes sense. Varys' story about him is a lie. Varys previously worked to keep the Lannisters on the throne-- he told Ned to give up his story about incest and false kings, not because he loves the Lannisters, but simply to keep the peace.

If Varys had always known of this child and always wanted to put him on the throne (which he at least implies he did), then he would told Ned to keep on pushing the "incest, false king" line. Which isn't what he did.

The whole story sounds like a recent idea, not one that's been in Varys' mind for 16 years.

Now, if Varys is lying, why lie? Kevan Lannister was about to die, and Maester Pycelle was already dead; why tell a lie to two dead men?

Well, those weren't the only people in the room. His spies/accomplices-- a gaggle of children -- were all present. He was telling them the lie, too. Likely, he wants it to spread. Aegon is coming; why not put out the word?

So where did they get this pretender from?

From books one and two. A boy was featured there, apparently for no reason, and then entirely disappeared from the series. That boy is Edric Dayne, nephew of the legendary Arthur Dayne. He has the Targaryen coloring (silver hair, purple eyes) just like this "Aegon." He was last seen riding with the Lightning Lord, but then split off from him for reasons that haven't been made clear yet. I think Arya ran into him.

I propose someone found him, discovered his Targaryen looks, and hostaed a plan to put a pretender on the throne.

Some of what Varys says about "Aegon" applies to Edric-- as Edric was riding as an outlaw, looking out for the common man (and children!) who suffer in war, he would, as Varys says of "Aegon," know what it means to struggle. While it's not true that he was always raised to be a prince, he is the son of a legendary (and honorable) knight, and squire to a Lord who seems concerned with the travails of the common man. The sort of person Varys might decide would make for a good king.

If Edric isn't Aegon, then why was he even in the books? I guess you could say that of 4000 other minor characters, but I think this is the solution here: Aegon is a pretender, to throw us off the scent of the real Lost Targaryen, Jon "Snow." (I don't know what his correct bastard name should be.)

I might be straining here, but the books keep mentioning the three-headed dragon. Maybe that's Aegon, Dany, and Jon. Three heads of the dragon Rheagon (though one is a false head).

Obviously this requires Jon Snow to survive his current difficulties, but I think that'll prove to be the case.

This then means the actual final conflict is not between Stark and Lannister (both houses already decimated), but between two Targaryen's, Jon Snow, bastard son of Rheagan, and Danyres, sister of Rheagan.

Which makes for a less than ideal war -- hero vs. heroine-- but then, the books seem to want to avoid the Good Guy vs. Bad Guy notion of war.

One More Thing: It was promised that if you stiff the Iron Bank of Braavos, suddenly you'll have pretenders vying for your crown.

Pretty sure Varys is from Braavos, or spent time there.

Well, the Lannisters stiffed the bank, and suddenly there's someone claiming to be Aegon Targaryen, fronted for by Varys. Who needs a patron, given that he had to flee his last one.