As seen in Sunday’s season-three premiere of Game of Thrones, Daenerys’s dragons aren’t so little or cute anymore — they’re more like a cross between a Komodo dragon and a Gremlin. And they’re growing fast. They’ll be prone to mood swings like most teenagers soon enough, according to Pixomondo’s VFX supervisor Sven Martin, who designed Dany’s fire-breathing babies for the show. Short of giving the three dragons acne, adolescence means big changes to the look of last season’s parrot-size creatures, and aging them up was largely a matter of capturing that mercurial teen angst. “The main idea for them this season was capturing the difference between how they look when they’re demure and when they’re threatening.” As babies, the dragons were able to dispose of the warlocks by setting them ablaze, but Martin said that was nothing compared to the terror they can now inspire. “We haven’t seen them really angry yet.”

The personalities of each of the three dragons will emerge more fully later in the season, but for now, Martin said to consider the black dragon, Drogon, the leader. “The other two are his wingmen.” Here’s a preview: A few episodes from now, Drogon will get a bit aggravated, and for that, Martin added features inspired by the well-documented reactions of “angry swans” and a famous movie beast. “One of the things that we played with that’s also new is frill and what it would look like when they’re mad. There are real lizards that have it. Or you may have seen it before in the first Jurassic Park, where the dinosaur is screaming at the guy in the car.”

Dany’s dragons were in happy and content mode in Sunday’s return, seen for the first time flying alongside her ship on its way to Astapor (and barbecuing their own mid-flight fish meal). They even look to Dany for some coddling, a behavior modeled after dogs. In fact, Martin said much of what makes up the dragons is inspired by real animals. Making them believable fliers, for example, was paramount to producers, and after more than a dozen different designs, the dragons were given a bat’s wingspan and the posture of an eagle mid-flight. “We wanted to keep it looking realistic, and of a realistic environment, which I think is the idea in Game of Thrones. It doesn’t look like a fantasy series, but of course it is one.”