In the world of George R.R. Martin, nothing embodies the lost age of magic quite like dragons. Yes, the Wall is impressive. Yes, the White Walkers are terrifying and the Children of the Forest are mysterious. But the dragons are larger-than-life, living fossils of the time before time. When Daenerys shows off Drogon, Rhaegal, and Viserion, she isn’t just solidifying her power. She’s calling upon ancient myths that states those who control dragons deserve veneration and royal status.
In modern vernacular, bow down bitches.
If you’re surprised by Drogon’s size compared to his siblings, indulge me in a brief and extremely incomplete history of dragon biology. According to ancient in-universe sources, dragons never stop growing. The largest of the Targaryen dragons was Balerion, better known as the Black Dread. Companion to Aegon the Conqueror when the Targaryen took over the Seven Kingdoms, Balerion grew so large his skull was the size of a carriage. The Black Dread died of old age after over 200 years. Rightly fearing such massive creatures, later generations of Targaryens put their dragons in cages and, in doing so, discovered it stunted their growth*. It turns out dragons only grow to fill the space they inhabit. This explains why Rhaegal and Viserion are smaller than their brother. Though now that the two dragons are free, they should eventually catch up in size.
*Dragon biology was also stunted by whatever calamity caused magic to seep out of the world.
With Game of Thrones barreling towards its conclusion, expect to see Dany and Drogon tear up the battlefield this summer. Hopefully, Viserion and Rhaegal will also find their rider and the three heads of the dragon will take down the Night King.