(Warning: The following contains major potential SPOILERS for future episodes/seasons of 'Game of Thrones' — albeit largely hypothetical ones — as well as mild spoilers for recently released episodes of the show. Proceed with whatever level of caution that suggests to you is wise.)
Now, here's the thing about dragons: Sure, they may look cool, and sure, they tend to strike fear into the hearts of your enemies, but when it comes to actually doing what the hell you tell them to? Not so much. Dragons, after all — as Tyrion Lannister has wisely pointed out in the past — tend to be far more intelligent than we give them credit for, making them a heck of a lot more difficult to domesticate than, say, a spaniel.
Which, seeing as they also have the ability to raze cities to the ground with their morning breath, makes them a pretty risky option as pets — and as weapons. After all, flame-throwers are dangerous enough when they aren't sentient and ornery. Adding wings and a bad temper really doesn't help all that much. And yet...
It Seems As Though We're Going To See Three Dragon Riders In Game Of Thrones
Specifically, it very much looks as though we're going to see Daenerys's three dragons — Drogon, Viserion and Rhaegal — wind up leading the charge in a future invasion of Westeros, with three of the show's human characters sitting astride their respective backs.
The main reason for that widely held suspicion? Well, that's just what Targaryens do with dragons in the Game of Thrones universe. Y'see, Daenerys's Targaryen ancestors first united the Seven Kingdoms from atop their dragon pals, with the Targaryen line having long been associated with the fiery beasts (and its dwindling fortunes often linked to the dragons having died out).
Why Does What The Targaryens Did Matter?
After all, as far as we know there's only one fully fledged Targaryen left hanging around in Game of Thrones, right? Daenerys Stormborn, Mother of Dragons, last of her line.
Except, of course, it seems that there are almost certainly some secret Targaryens out there — and they might well already be being lined up to ride Viserion and Rhaegal, while Dany takes the reins atop Drogon.
Here's the logic...
(And note, here's where those aforementioned major SPOILERS really start to kick in.)
Jon Snow Is Probably A Targaryen
Remember that whole R+L=J theory the internet has been going crazy over for years now? Well, the full logic behind it is a little too extensive to go over in one paragraph — you can pore over its minutiae right here though — but suffice to say that it would, if true, make Jon Snow the (possibly legitimate) son of Rhaegar Targaryen and Lyanna Stark.
Which, if true, would make Jon Daenerys's nephew, and a likely candidate to ride one of her three dragons into battle, seeing as his inner Targaryen-ness could well allow him to do so. What's more, with one of the three — Rhaegal — named after his (theoretical) father, he's already got his steed picked out for him.
What About The Third Dragon, Though?
Specifically, if we assume that Dany would ride Drogon, and Jon Rhaegal, then who could we see astride Viserion in that widely anticipated final dragon-centric battle?
Well, if an entirely different Targaryen-themed rumor is to be believed, it could be... Tyrion. With Tywin Lannister having spent much of his time on screen reiterating that Tyrion isn't his son, it's not all that surprising that a fan theory has long since emerged to explain that, in actual fact, Tyrion may not be Tywin's son at all. Instead, he might just be a Targaryen, with his father being the Mad King, Aerys.
Which, if true, would make Tyrion Daenerys's older brother, and Jon's uncle, and a likely rider for Viserion. Indeed, the show's recent revelation that Viserion and Rhaegal have a grudging respect for (or at least a willingness not to eat) Tyrion would seem to support this.
What If Those Theories Don't Turn Out To Be True, Though?
After all, both of those theories rely on fairly big plot twists that are strikingly similar to one another — something Game of Thrones may be unwilling to do. Tyrion's heritage, in particular, could fall by the wayside in the face of fan support for seeing Jon Targaryen emerge into the light of day.
If not, then, could we perhaps see a less obvious candidate take to the skies atop Drogon, Viserion or Rhaegal? Bran Stark has long been mooted as a potential rider, using his warg-ing abilities to control, say, Viserion — something that would allow him to fly, even if he still couldn't walk. Intriguingly, Varys has also been offered up by some as a potential Targaryen, something that would certainly explain his devotion to Daenerys's cause (and make him a perfect non-threatening ally for the throne, what with his being a eunuch and all).
In the end, though, it seems that we could have a pretty long wait to find out — with any actual dragon riders unlikely to come to the fore until the show's final season.
In the meantime, then...