For a man who still has two whole books to write, George R.R. Martin sure has a lot of time on his hands. So much, in fact, that he's been able to ponder the changes made from the source material in Game of Thrones, and he's shared the changes he would make to the show with the New York Times.
Any fan of the series A Song of Ice and Fire will tell you about the plethora of scenes that were cut from the show. In an interview with The Times, Martin suggested that extending the series to 13 episodes a season would leave time for some smaller moments; for example, Martin mentions a scene from season one where Sansa and Arya had an argument which was cut. Although the scene doesn't move the plot along, it helps establish the girls' characters. And Martin has been pretty vocal about changes he would make to the show's costume and design, particularly the Iron Throne.
Most importantly, Martin does a good job of explaining how changes from the source material can create a sort of "butterfly effect," causing more changes to have to be made later in the show. For example, Martin talks about how the singer Marillion having his tongue cut out in Season 1 affected the show. In the books, Marillion became the scapegoat for the murder of Lysa Arryn, but in the show, he's never seen again and it's simply declared a suicide.
But that isn't the only small change that's affected the show. Here are some of the small changes that have later created a serious divergence from the source material:
In the book, Shae is a little less "strong-willed prostitute" and a little more "ditsy gold digger." Making her more sympathetic in the show was a seemingly insignificant change ... at first. But it meant that Tyrion had to pull a Harry and the Hendersons on her and pretend he didn't love her so it would make sense for her to testify against him later. In the book, Cersei just shows her some gold and she more or less goes "Okay!" But this decision did make it all the more emotionally wrenching.
Y'all remember Edric Storm? No, of course you don't, because in the show, he never even exists. But in the books, he makes a small, but important contribution: the Red Priestess, Melisandre, sacrifices his blood to kill off the other claims to the Iron Throne. In the show, they didn't want to introduce yet another character, so instead they used one of Robert Baratheon's bastards we already know: Gendry.
But in the books, Gendry takes a completely different path, joining up with the Brotherhood Without Banners as a blacksmith and eventually having an important chance encounter with Brienne of Tarth. The showrunners may have solved this one, but again, it involves yet more changes to the source material...
Biter and Rorge Die
Ah yes, Biter. The lovely member of the Brave Companions who enjoys biting off human flesh. In the show, he and his friend Rorge have a run in with Arya and The Hound, who end up killing both of them. But (possible spoiler alert?) that encounter actually happened with Brienne, whose face gets badly bitten by the gruesome Biter. Arya and The Hound actually kill two different members of the Brave Companions, The Tickler and Polliver. So now the question is, how will those characters die now and what will happen to Brienne next season?