What hints do the prequels give about the main series?

[Lion of Lorath]

For example, Baelor Breakspear is a Targaryen with a Dornish mother, and he looks Dornish rather than Valyrian-- thus the child of Rhaegar and Elia would also look Dornish, which proves that Aegon is an imposter (whether he knows it or not.)

Any other hints at various things?

[Eiko Dragonhorn]

For example, Baelor Breakspear is a Targaryen with a Dornish mother, and he looks Dornish rather than Valyrian-- thus the child of Rhaegar and Elia would also look Dornish, which proves that Aegon is an imposter (whether he knows it or not.)

Any other hints at various things?

Baelor had at least 2 brothers with Valyrian looks.

Aegon was known to have been born with the characteristic silver hair.

So that was a terrible example. But there are plenty of good hints in there.

[kissdbyfire]

For example, Baelor Breakspear is a Targaryen with a Dornish mother, and he looks Dornish rather than Valyrian-- thus the child of Rhaegar and Elia would also look Dornish, which proves that Aegon is an imposter (whether he knows it or not.)

Any other hints at various things?

The fact that a Targaryen + Martell offspring can have the Martell phenotype doesn't mean that all offspring of these two bloodlines will always have the same appearance.

[pettes]

Aegons sister even have the dornish look

[Mithras]

History of the Blackfyres.

Even a random hedge knight is given a fair trial when he struck a crown prince (compare that to Rickard/Brandon).

Bloodraven.

Egg.

Probably more material about the TPtwP prophecy in the future D&E novellas.

And lots of other world building stuff that has direct relevances to the main series.

[RedShirt47]

Egg shaves his head to hide his distinctive Targ hair could hint at Varys doing a similar thing.

Dunk has many parallels with Brienne.

[Lost Melnibonean]

The eggs hiding, and hatching into, dragons... like this...

http://asoiaf.westeros.org/index.php/topic/128072-peeling-another-egg/

[Good Guy Garlan]

Aegon + Sansa, per the Ashford Tourney

Also, it is heavily implied that House Frey (more specifically Walder's dad) betrayed the Blackfyre loyalists at Whitewalls. And it could be why in aDwD Haldon says that House Frey is long renown for treachery.

So it seems to me that Team Aegon won't go easy on the Freys

[Valyrian Fork]

The "Dragonfly" amongst the "Reeds" that "looks nothing like a dragon". If that's not a red herring or coincidence, that one is going to be absolutely enormous.

[aryagonnakill#2]

Ya there's no need to talk about Dornish looks vs Valyrian looks, the fact that we are given the whole backstory of the Blackfyres is plenty.

As said above Varys pulling an egg, and possibly Ashford.

Another is simply the fact that dragon in prophecies often means Targ, not an actual dragon. Could come into play.

[Lost Melnibonean]

The problem with the bald as an egg thing is that Pycelle's head, Ebben's head, and Caleotte are all described in similar terms.

[aryagonnakill#2]

^None of them are secretly trying to put Targs/Blackfyres/ whoever's on the throne.

[Lost Melnibonean]

^None of them are secretly trying to put Targs/Blackfyres/ whoever's on the throne.

True. But the hint would be stronger if The George didn't use that particular description as muchvas he does, and if Varys didn't also need to keep his head shaved in a mummer's cut to slip easily into his disguises.

[Valyrian Fork]

^None of them are secretly trying to put Targs/Blackfyres/ whoever's on the throne.

Actually Caleotte might be? It's entirely possible he knows what Doran is up to.

[Addam of Hull]

Egg's eyes being so dark purple, they appear black... which links back to Jon, whose eyes are described as being a gray so dark, they look black.

[Red Rahloo Connington]

The "Dragonfly" amongst the "Reeds" that "looks nothing like a dragon". If that's not a red herring or coincidence, that one is going to be absolutely enormous.

Wow. I remember this quote vividly, I never gave it a second thought. Who/what do you think it refers to?

Now the prince dunk being an ancestor to the reeds theory has something to back it up. But it can easily be anything else.

[Lion of Lorath]

Baelor had at least 2 brothers with Valyrian looks.

Aegon was known to have been born with the characteristic silver hair.

So that was a terrible example. But there are plenty of good hints in there.

Which brothers had Valyrian looks? Aegon's mother wasn't Dornish though, she was a Dayne and who knows how much Targaryen blood she had in her; just look at Edric Dayne for an example of how Targ-like the Daynes can look.

[Mithras]

Which brothers had Valyrian looks? Aegon's mother wasn't Dornish though, she was a Dayne and who knows how much Targaryen blood she had in her; just look at Edric Dayne for an example of how Targ-like the Daynes can look.

Most probably none. I think George confirmed in an SSM that the Daynes do not have Targaryen blood.

[Red Rahloo Connington]

Which brothers had Valyrian looks? Aegon's mother wasn't Dornish though, she was a Dayne and who knows how much Targaryen blood she had in her; just look at Edric Dayne for an example of how Targ-like the Daynes can look.

Maekar and Aerys had the Valyrian look

[Eiko Dragonhorn]

Which brothers had Valyrian looks? Aegon's mother wasn't Dornish though, she was a Dayne and who knows how much Targaryen blood she had in her; just look at Edric Dayne for an example of how Targ-like the Daynes can look.

Aerys and Maekar, we never get a description of Rhaegel but he might too.

I was talking about Aegon VI, not Aegon V, since that's the one you mentioned in the OP.