When Game of Thrones concluded in 2019, fans thought they'd seen the last of Jon Snow. However, that may no longer be the case following The Hollywood Reporter exclusive that a live-action Jon Snow sequel series is in the works, with Kit Harington set to reprise his role.
Seeing as Jon was not the only character to survive the series, it is likely that many other familiar faces will appear in the sequel story. The familiar characters most likely to appear are not just those who survived, but those who already have a meaningful connection with Jon and who would have a good reason to return in a story focused on him.
Tormund Giantsbane
The Game of Thrones finale ended with Jon journeying North beyond the Wall with Tormund Giantsbane and the other surviving Free Folk. Tormund became a loyal friend and ally of Jon and was right beside him at the end of the series. In fact, Tormund even waited at Castle Black and waited to return home with the other Free Folk until Jon arrived at Castle Black.
Any sequel story with Jon has to include Tormund. It would also be interesting to see how their friendship has grown now that the thing that brought them together--their common enemy of the Army of the Dead--has been vanquished.
Ghost
While most of the direwolves sadly did not survive Game of Thrones, Jon was fortunate enough to reunite with his direwolf Ghost in the series finale, with both characters overjoyed to see each other again. Ghost joined Jon and the Free Folk as they ventured North of the Wall.
Many fans were disappointed that the direwolves were seen less during the later seasons of Game of Thrones. Showing more of Ghost and more of his unique relationship with Jon can partially rectify that. More focus on Ghost could also reveal Jon being a warg through Ghost's mind (a fascinating part of Jon's story from the books that was never explored in the show).
Sansa Stark
While fans felt bad for and hated Sansa Stark at many different points, one of the few things about the Game of Thrones ending that almost all fans liked was Sansa becoming Queen in the North. This felt like a natural and earned culmination of her story arc.
The North is now its own kingdom and is independent from the rest of Westeros. It would be interesting to see if Sansa wants the independent North to have any relationship with the North beyond the Wall. She and Jon love each other, but they have also had their share of issues in the past. Disagreements on the North versus the North beyond the Wall could be a source of conflict between Jon and Sansa in this series (although they could just as easily be allies).
Drogon
Drogon is the last dragon in the world and Jon Snow is the last Targaryen. They've already bonded in the past, with Drogon trusting Jon in a way he never trusted anyone but Daenerys. However, after the important death of Daenerys and Drogon burning down the Iron Throne, Drogon flew off, with his whereabouts unknown (other than Samwell Tarly mentioning that he'd been seen flying east).
Drogon's unresolved fate and Jon's connection with him makes it likely that the dragon would appear in the sequel series. While Jon knows he had no choice but to kill Daenerys, he will probably still be wrestling with grief and regret, which will become even more complex after a reunion with Daenerys' favorite dragon.
Bran Stark
One of King Bran's first acts was to exile Jon and have him join the Night's Watch at Castle Black. This was a compromise made between Grey Worm wanting Jon dead for the murder of Daenerys and Sansa and Arya wanting Jon to be a free man. It didn't end up being much of a punishment as Jon didn't stay at Castle Black and got to join Tormund and the other Free Folk beyond the Wall (with Jon finally getting the peace and freedom he'd long sought).
Jon's last words were apologizing to Bran for not being there when Bran needed him. Bran's reply was, "You were exactly where you were supposed to be." Given Bran's abilities as the Three-Eyed Raven, he may have sent Jon to Castle Black knowing that Jon would be needed beyond the Wall in the future. Given that Jon regrets not being there more for Bran, it is also possible that Jon could return to help Bran as well.
Samwell Tarly
Sam is Jon's best friend and it would be a missed opportunity to have a sequel series without seeing their friendship again. After going through so much together during seasons 1-5, they were separated during seasons 6-7. They shared some scenes together in season 8, but there wasn't enough time to do their friendship justice with everything else going on in the final season.
The sequel series will likely have more room to breathe than the final season of Game of Thrones, thus giving more opportunity to do their friendship justice. Jon may be beyond the Wall and Sam may be serving as Grand Maester in King's Landing, but neither of them would hesitate to travel far if it meant helping each other.
Tyrion Lannister
As characters treated like outsiders in their own families and by the world around them, Jon and Tyrion quickly became friends during season 1 of Game of Thrones. While they wouldn't see each other again until season 7, their relationship was definitely important to the endgame of the series.
Beyond being treated like outsiders, they are both good men who want to help others and who want to atone for their mistakes. They are each doing this in their own way, with Tyrion being Hand of the King, and Jon exiled but at peace. Their relationship and the similarities in their respective journeys are too rich and too similar to have them never meet again.
Davos Seaworth
Jon quickly earned the respect of Davos Seaworth. After the death and defeat of Stannis and the resurrection of Jon, Davos became Jon's most trusted advisor. He helped gather Northern houses such as the Mormonts in the fight against the Boltons, fought alongside Jon during the Battle of the Bastards, and traveled with Jon to Dragonstone to help convince Daenerys to join the fight against the Army of the Dead.
Davos is now serving King Bran as the Master of Ships. Just like Sam and Bran, Davos is not geographically close to Jon, but his strong connection to Jon makes it feasible for him to return.
Brienne Of Tarth
Brienne of Tarth and Jon Snow spent a lot of time around each other and were on the same side during the final seasons of Game of Thrones. Yet, they never interacted with each other much and didn't have any kind of relationship with each other.
They are similar characters in that they believe in loyalty and honor and they value these traits above all else. Seeing two of the best swordfighters and noblest warriors getting to team up in a sequel series would be a dream come true, made even better now that Brienne is a knight and the Lord Commander of the Kingsguard. Also, if Tormund is still by Jon's side, he would certainly be happy to see Brienne again.
Arya Stark
Of the surviving Starks, Jon definitely has the closest relationship with Arya. Her decision to explore what is west of Westeros and to sail into uncharted territory means she is far away from Jon.
Given the vast distance between them, it could be logistically challenging for Arya to appear in this story, even more challenging than the distance between Jon and the characters in King's Landing. However, if Jon needs Arya or she needs him, both of them would be willing to travel any distance necessary.