The last episode of the series saw Daenerys' dragon Rhaegal killed by Euron Greyjoy, while her third dragon Viserion was killed alongside the Night King. But according to the theory, Drogon, who was notably missing in action for a large chunk of time back in season 5, might actually be female and might have given birth to a whole fleet of baby dragons. Other people have long theorized that GoT dragons are genderless and can all procreate.
“This theory says that in the fifth season, when Drogon spends almost a whole season gone, he’s actually laying eggs and is, in fact, a female,” theorizes u/Justzxcvbnm. “That’s why he was burning fields full of sheep, goats and etc. to feed the baby dragons. He’s the only one who disappeared, the only one who drove herds and took them all like roasted sheep.”
The teaser for episode five gives weight to this theory. In one scene, Euron can be seen looking up a the sky, eyes with fear as a dragon screeches. Considering he's already seen Daenerys’ dragons and knows there’s just one left, he presumably wouldn’t react like this upon seeing only Drogon - leaving many to believe there's more.
Watch the moment below: