Game of Thrones has built such a complex world of history and mythology over the past seven seasons that fans have come up with all kinds of theories about certain characters. While some theories are so wild as to be quite unlikely, others have proven to be true. One big theory that has been circulating among fans of the show and the A Song of Ice and Fire book series for years has been that Tyrion Lannister isn't actually a Lannister. Instead, he's a Targaryen and destined to ride the third of Dany's dragons. Now, the latest episode of Game of Thrones may have sneakily confirmed that the Tyrion-as-secret-Targaryen theory is actually true, and it was in a scene that didn't feature Tyrion at all.
When Dany returned to Dragonstone in "Eastwatch" after roasting the Lannister army on Drogon, she encountered Jon Snow as he was brooding on a cliff. Instead of fleeing from the giant black dragon to continue his brooding elsewhere, Jon turned around and looked Drogon in the eye. Drogon leaned his head down and allowed Jon to touch his snout. Dany was clearly shocked that Drogon of all her dragons was allowing somebody else to touch him, as it was something she'd never seen since her dragons had grown to full-size. For her, this was something entirely new. For fans, it was a reveal of just how Jon's likely status as Rhaegar Targaryen's secret son will probably come in handy. As it turns out, Dany's dragons are just fine with Targaryens getting close.
Therein lies the clue that Tyrion isn't the son of Tywin Lannister. While he didn't have any close encounters with any of Dany's dragons in "Eastwatch," the moment of Jon not getting killed by Drogon echoes the moment back in Season 6's "Home" when Tyrion was not killed by Rhaegal and Viserion. At the time, Dany was absent from Meereen with Drogon, and the other two dragons were chained underground and refusing to eat. Tyrion, unwilling to let Rhaegal and Viserion starve themselves to death, ventured down into the darkness to unchain them. Against all odds, the dragons allowed Tyrion to get close to them, touch them, and even tell them a story as he worked to break their chains. Rhaegal and Viserion let Tyrion get close, just as Drogon would later let Jon get close.
With these two moments, Game of Thrones may have confirmed the fan theory that Tyrion is a secret Targaryen, much as Jon is. If Drogon liked Jon because of his Targaryen blood, it stands to reason that Rhaegal and Viserion like Tyrion for his Targaryen blood. That said, if Tyrion truly is a Targaryen, the show hasn't addressed how or why another major character just so happens to be related to the bloodline that is supposed to be all but extinct. For those answers at this point, we can turn to the books.
Warning: spoilers ahead for the A Song of Ice and Fire book series.
In George R.R. Martin's saga, he gives more background on the Lannister family than has been revealed on the show. The books reveal that the Mad King Aerys had his eye on Joanna Lannister when she was at court during Tywin's tenure as Hand of the King. She would leave King's Landing to live at Casterly Rock with Jaime and Cersei, away from Aerys wandering eye, but their paths would cross again when Joanna attended a tourney in King's Landing. The very next year, Joanna died giving birth to Tyrion, who bears little resemblance to Jaime and Cersei.
The timing could have worked out for Aerys to have forced himself on Joanna in King's Landing and fathered Tyrion. Tywin couldn't prove that Tyrion wasn't his after Joanna's death, and he might not have wanted to bring shame to his dearly departed wife even if he could prove that he wasn't the father. Tyrion as the Mad King's son could explain why Tywin so despised his youngest child. Yes, the stated reason was that Tyrion was a dwarf and not another golden warrior like Jaime, but perhaps there was more to it. If the show is to follow the history of the book saga, the question of how Tyrion could be a secret Targaryen is relatively straightforward: he's Dany's older half brother by the Mad King Aerys.
Aerys fathering Tyrion could explain how we'd get a second secret Targaryen, but it doesn't address why George R.R. Martin would bother with such a thing. The answer to that question comes from one of Dany's visions in the House of the Undying. She visited the House of the Undying in the books as she did in the show, although her experiences were quite different. In the A Clash of Kings novel, Dany sees into the past, when her brother Rhaegar was speaking to his wife Elia after the birth of their son, Aegon. Rhaegar claimed that Aegon was the prince that was promised, then said that "the dragon has three heads" in prophecy.
Rhaegar's original vision for the three heads of the dragon were his son Aegon as the prince that was promised, his daughter Rhaenys, and a third child, who would ultimately be Jon Snow, although too late for Rhaegar. If Game of Thrones decides to incorporate the three-headed dragon prophecy on top of the Prince That Was Promised/Azor Ahai prophecy, then it stands to reason that the show will need a third "dragon" to join Dany and Jon. If Tyrion is indeed a secret Targaryen, he would fit the prophecy. We could very well have three characters with Targaryen blood riding dragons by the end of the series: Dany on Drogon, and Jon and Tyrion on Rhaegal and Viserion.
Obviously we can't say at this point if the show will delve into the prophecy of the dragon with three heads, although a certain plot twist in "Eastwatch" gives the impression that we could be in for a lot more information about Rhaegar in what remains of the series. What we can say is that Tyrion in the book and the show had a childhood fascination with dragons, Tyrion in the book and the show looks quite different from his siblings and Tywin, and the show gave Rhaegar's son a scene that quite closely mirrors a scene that already happened with Tyrion.
If Game of Thrones reveals that Tyrion is a secret Targaryen, at least we can't say that there weren't signs along the way. Who knows? Maybe the fact that Dany, Jon, and Tyrion all lost their mothers in childbirth will turn out to be relevant. That said, it's possible that Game of Thrones will give Tyrion a connection to dragons without connecting his bloodline to the Targaryens. Stranger things have happened.