Due to the length of Game of Thrones, a lot of arcs never really got tied up:
- In the first season finale, Grand Maester Pycelle is shown to be mostly feigning his "harmless little old man" persona, and is shown striding around his quarters with a fair bit of energy for a man his age, before slowing down and assuing his familiar hunch when leaving his room. The scene sets up that he's employing Obfuscating Stupidity and is actually much more alert and strong than he lets on, but nothing ever comes of it. A cut scene would have had him letting down the ruse around Tywin and explaining he acts this way so he can enjoy the privileges of his station without any of the schemers and politicians around him seeing him as a threat. Either way though, nothing comes of this and Pycelle spends the series act like a loyal tool of whomever is in charge, never enacting any plans nor taking a major role in anyone else's plans.
- In Season 2 Sam finds a cache of dragonglass weapons and an old horn. In the books, it is heavily implied that this is the legendary Horn of Winter, which can bring down the Wall when blown, and Sam is repeatedly mentioned to still have it with him as he travels. In the show, the horn never appears again.note
- As Daenerys' dragons grow, she has trouble controlling them and Drogon in particular becomes rather nasty and even briefly snapped his jaws at Dany when she interrupted him eating. This is totally dropped in Season 6: Drogon returns after abandoning Daenerys at the end of Season 5, and for the rest of the series Dany has no problem controlling them and they respond to vocal (if not downright telepathic) commands perfectly.
- The whole point of the series-long subplots involving the Iron Islands is that they wanted to be independent of the Iron Throne and be their own kingdom again. In Season 6 Yara forms an uneasy alliance with Daenerys, and in Season 7 Euron pledges himself to Cersei, and the independence of the Iron Islands is never brought up again. Yara is even present in the series finale when Sansa declares the North's secession, and says nothing of the Iron Islands.
- In Season 4, Bronn is set to marry Lollys Stokeworth and join the petty nobility. He was originally going to stick around King's Landing and begin quietly eating up Cersei's influence around the city, but Lena Heady and Jerome Flynn's messy breakup prevented the pair from acting in any scene together going forward. Instead, Bronn is unceremoniously dumped by the Stokeworths and follows Jaime to Dorne as a simple hired sword once again.
- In Season 4, Sansa and Littlefinger were in effective control of the Vale and it was heavily set up that Sansa was ready to become a more active player in the game of the thrones, including her blackmailing Littlefinger with the truth of Lysa's death and defying his instructions to use a well-crafted lie to hide her identity from the Vale lords. In Season 5, Littlefinger convinces Sansa to marry Ramsey Bolton, and Sansa never returns to the Vale nor takes part in Littlefinger's schemes again (especially since such a monumentally stupid act convinces her that he's her enemy and she can't trust him).
- Near the end of Season 6, Sam stole Heartsbane, his family's ancestral Valyrian steel sword, to use in his studies at the Citadel. He also took it in order to piss his father off and openly expected Randyll to hunt him down to try and take it back. However, in Season 7 when Sam is studying at the Citadel he never makes any mention of having Heartsbane or using it for anything, Randyll is never mentioned to want his sword back, and Randyll and his son Dickon are executed by Daenarys, making the sword Sam's by right anyway. Sam ends up giving the sword to Jorah in Season 8, mostly just so he can have a valyrian steel weapon to wield against the White Walkers.
- Dorne pretty much vanished as a region after Season 5. In Season 6 Elarra and the Sand Snakes seize control of Dorne by killing Doran and Hotah, and are not seen until the end of the season, and then the second episode of Season 7 sees them all Put on a Bus either by killing them off or having them imprisoned by Cersei, and most of Daenerys's support from Dorne is erased with them. By the end of the series, Dorne was of such little importance that its new prince (who only appeared in the series finale) wasn't even given an identity; the actor assumed he was playing a younger brother of Oberyn and Doran.note
- Towards the end of Season 6, it's implied that Margaery's newfound faith in the Seven may be an act while she prepares something for the High Sparrow and Faith Militant. All involved parties are killed when Cercei blows up the Sept of Baelor, before this plot line can resolve.
- Season 7 has Sansa express concern about how the northlands will feed so many people with Daenerys's army allied with them, and it was also a plot point that the Lannisters had raided the Reach for supplies. For that matter, the fear of starvation in the face of winter approaching was an on-going subplot through most of the series. However, no actual supply problems occur in the later seasons, and mass starvation or tired and hungry armies are given token mentions but don't actually occur. This goes hand-in-hand with large armies suddenly able to march great distances in a short amount of time without concern for the logistics behind their journey.
- Season 6 adapts a condensed version of the Riverlands subplot from the books concerning the Freys and the Tullys and the siege of Riverrun. The Freys were last seen massacred by Arya at the start of Season 7 and the Riverlands, much like Dorne, were never mentioned again until the series finale, when Edmure shows up with the other lords of the Seven Kingdoms.
- Seasons 5 and 6 both showed priests of R'hllor championing Daenerys around Essos and preaching about her to others. Dany sailed for Westeros at the end of Season 6 and Essos was never seen again, and any influence the Red God and his priests may have had on her or in Essos was never touched upon. This is particularly glaring since Tyrion specifically sought out a priestess to try and raise support for Daenerys in the region, and nothing was ever said of it again.
- A major subplot in mid-seasons is the Crown's massive debt to the Iron Bank of Braavos, owing them millions they can't afford to pay, and with the Lannister gold mines gone dry, the Seven Kingdoms is facing an economic crisis. Come Season 7 when Cersei captures Highgarden, the Tyrells apparently have enough to pay off the Bank at once and they're never mentioned again, nor are the economic troubles of the Crown.note
- Season 7 makes a point about Jon Snow's resurrection being something of importance, with Jon stopping Davos from letting it slip to Daenerys and her questioning about it, as well as longing looks at his injuries, implying that this was going to have some degree of importance in the following season. It doesn't, and in fact, while Jon and Daenerys become intimate, no word is ever referenced to the secret he was keeping about his partially undead nature.
- Jon points out how ridiculous it is to Daenerys, that she took the word of Mirri Maz Duur, a vengeful woman who had cause to be petty, that Dany couldn't have children anymore, this seems like it may have led to Dany being pregnant with Jon's child, but ultimately with Danys death, it went nowhere.
- The fifth season introduces the kingdom of Dorne and establishes a new storyline about political intrigue revolving around Prince Doran and his nieces, the "Sand Snakes." The comparable storyline from the books has the Sand Snakes plotting against Doran after he fails to side with them against the Lannisters, but he eventually outwits them and reveals he has a complex, large-scale plot in mind to betray the Lannisters at the most inopportune moment for them by siding with Daenerys Targaryen. However, in the TV series the Dorne plot of Season 5 was widely despised, causing the writers to switch gears and simply murder most of the Dornish cast in the opening episode of Season 6, with the survivors returning in a minor role in Season 7. Actor Alexander Siddig (Prince Doran) even noted his confusion at being told of a long-term, multi-season story for his character only to be brutally killed off at short notice.
