To start with, I thought I’d just lay out some things to think about in terms of alternate history:
- Points of Divergence - you need to think carefully about what event you’re changing, because the events before that will structure the environment and historical forces that will shape your PoD. And in general, it’s a good idea to try to stick to one PoD so that the effects of the change can be considered in isolation.
- Historical Forces vs. Contingency and Agency - this goes to a philosophical tension within the discipline of history. Historians acknowledge that long-term forces (economics, society, culture, religion, demographics, climate, etc.) have a huge influence on the course of events, but at the same time, it’s equally clear that both individuals and groups have agency in history rather than being the mere puppets of social forces, and do things that overturn historical forces or create brand new ones. It’s especially important to look for contingent events or phenomena (they make good PoD) - if Bran decides to climb a different tower that day, well... [so you mean the great man theory of history vs the counter argument to that? yah, sort of. but it goes beyond that; it’s more an argument against the “longue duree” camp and a particular camp of materialist Marxist historians about whether you can just base everything off of long-term trends]
t- The Butterfly Effect - small things can have a huge effect on the course of events, over time, so a change to the past should have cascading effects in the future. One of the big sins of alternate history is to make a change and then try to shoehorn in events from the original timeline even though the change may mean they never happen. If Rhaegar overthrows his father at the Tourney of Harrenhal, we shouldn’t assume that Balon Greyjoy is going to attack the North in 299 AL just because it happened in the books.

[That’s true and worth mentioning at the start, though at times we may have to minimize the effect for our calculations because 1) we don’t know exactly how it would work, because we inherently can’t 2) we could say that about almost any change and would just keep saying it every time with every what if]

--Another thing to add is is author’s intentions. Sometimes the author just needed something to happen a certain way for his/her overall story plan. Because the book has a known“God” (author) whereas history is agnostic. Again something we will have to ignore because we don’t care about the author’s intention here, so we are in a way treating the book like history (without a god/author) to do a proper what if episode and enjoy doing it.

[Agreed, which is why I like to talk about GRRM as the gods in a Greek tragedy; things will go just enough wrong or right in order for what he wants to happen to happen. Which in turn helps us to understand where the key turning points are]

In a Setting like ASOIAF, where personal relations drive everything, persons are important for counterfactuals. For the outbreak of the Industrial Revolution, on the other hand, they get pretty meaningless. It depends mainly on the level - the more macro you go, the less important persons become. Since the story is pretty micro, taking place in only two or three years, the structures aren’t that important.




So here’s a preliminary list of the biggest or more interesting what ifs in the books:

AGOT:
- Bran doesn’t get thrown from the tower/picks another tower to climb?
- Catelyn hadn’t gone to King’s Landing and had sent someone else instead?
- Catelyn or Eddard had visited Dragonstone, as both planned to do at various points (her on the way to KL, him after resigning)?
- Eddard checked out Littlefinger’s story about the dagger, or just asked Renly, etc?
- Catelyn and Tyrion at the Inn - what if they’d never met, what if they’d met at Moat Cailin, what if she’d gone west to Riverrun or north to Winterfell instead of to the Eyrie?
- Eddard hadn’t stopped to talk to LF after resigning? [yes --related question, Eddard leaves to rally the men rather than make a play at King’s Landing -- related to that, eddard sends the girls away before making his move]
- Tyrion doesn’t make it to the Lannister camp (either b/c of the duel, the mountain clans, etc.)?
- Eddard hadn’t gotten injured in the fight outside the brothel?
- Robert hadn’t gone hunting or just didn’t encounter the boar?
- Eddard keeps his yap shut instead of talking to Cersei, or has her arrested in the godswood?
- Ned takes up either Renly or LF’s offer?
- Catelyn had negotiated for something other than Robb’s hand? Robb had gotten married on the spot?
- Robb decides to go after Tywin rather than Jaime?
- Robb gives command of his foot to someone other than Roose Bolton (Greatjon or Galbart Glover or Robett Glover, etc.) I want that!
- Eddard isn’t executed? // What if Eddard was sent to the wall as planned?
--What if jumped into the crowd (crowd surfing)
- Robb declares for either Renly or Stannis?
- The Lannister’s call for allegiance is answered? I want to write an article about this for some time now: at the end of AGOT, the Lannisters send a swarm of ravens demanding allegiance from Renly, Stannis, Highgarden, Pyke, etc. None of which is answered. But what if it had?



ACOK:
- Robb doesn’t send Theon to the Iron Islands?
--What if Catelyn had been in Winterfell when Theon went there (Feathered Hat Theory) 1) Maybe prevent the loss with more men kept there 2)Hostage or Marriage (theon, victarion)?[that’s a good one]
- Tyrion had swapped the different offers from the “one, two, three”?
- Renly and Catelyn had sealed an alliance prior to his murder?
- Stannis attacked King’s Landing first before Storm’s End? (while the chain and WF not ready)
- Theon doesn’t take Winterfell (either b/c he sticks to the plan or Rodrick doesn’t send all the Winterfell guard to Torrhen’s Square)?
- Arya names someone different?
- The riot after Myrcella’s send-off goes even worse?
- Stannis gets to KL earlier (doesn’t stay to take Storm’s End)?
- Edmure fails to prevent Tywin crossing the Red Fork? or delays him for just long enough that Tywin doesn’t make the rendevous at Tumbler’s Falls, or in time to get to KL before Stannis can breach the walls?
- Arya reveals herself to the Northmen when she helps them seize Harrenhal?
- Catelyn either doesn’t let Jaime go or does a proper exchange of hostages?
- Ser Mandon Moore kills Tyrion/Tyrion dies of his wounds?
- Sansa leaves KL with the Hand?

ASOS:
What if Oberyn won the duel?

Pregame of thrones: What if Rhaegar got away from the Trident [ 2 scenarios: Draw and retreat, loss but Rhaegar gets away with a few men] And what if the battle went the other way? (arthur dayne at the trident)

----------------------------------------------
Marriage parings, what would have happened?

Ned and Cersei [aching loins]

Robb x Asha

Roose x Catelyn after Ned’s death

Walder Frey x Catelyn

Stannis and Cersei [goes to bed like the battlefield]

Jaime and Lysa

Jaime and Cersei

Blackfish x Loras

Catelyn and Brandon

Littlefinger and Lysa (back then)

Littlefinger and Catelyn (impact on the realm)
Viserys and Arriane

Theon x Catelyn


------------------------

ADWD ones from the forum:

What if Tyrion had not convinced Aegon to go west?
What if Jon had fought Tormund Giantsbane?
What if the Shavepate/Greyworm/Barristan catched the red flux?
What if Stannis would not have freed Deepwood Motte but went straight to Winterfell after convincing the clans?
What if somebody had revealed that Fake-Arya is fake?
What if Walder Frey died before the wedding in Winterfell?
What if the Iron Throne did not believe Manderly?
What if Jon had not ordered all of his loyalists to go away?
What if Quentyn had not decided that he need to steal a dragon (or his friends stopped him)?
What if Tyrion had managed to meet Dany and finally seen a dragon?