In the very first episode of Game of Thrones, "Winter Is Coming," Illyrio Mopatis (Roger Allam) gifts Daenerys Targaryen (Emilia Clarke) three petrified dragon eggs from the mysterious Shadow Lands beyond Asshai at her wedding to Khal Drogo (Jason Momoa). "The ages have turned them to stone, but they will always be beautiful," Mopatis tells her. By the end of the season, both Dany's brother Viserys (Harry Lloyd) and the Khal are dead, but Daenerys emerges from Drogo's funeral pyre with three newly hatched dragons, the first to be born in hundreds of years. Daenerys names her dragons Rhaegal, Viserion, and Drogon.
Spoilers through the end of Game of Thrones Season 7 ahead!
Dany's Dragons: Rhaegal
Daenerys' dragon Rhaegal is named for Rhaegar Targaryen, Daenerys' oldest brother and father to Aegon Targaryen (who we know better as Jon Snow). His scales are green and bronze. Rhaegal has no rider (yet), but frequently accompanies Daenerys, including to the Dragonpit, where Cersei correctly deduced that something had happened to one of Dany's dragons.