Spoilers for Westworld Season 3 Episode 2 follow below.

Fans of Westworld were treated to a Game of Thrones-sized treat in Season 3 Episode 2, titled “The Winter Line.” While the episode revealed an all-new park, the 1940s-set Warworld, we also followed Bernard and Stubbs into The Mesa where yet another new park was revealed. This one has a fantasy tinge to it, and who better to underline a fantasy park than Game of Thrones showrunners David Benioff and D.B. Weiss?

Indeed, the episode offered a brief glimpse at Benioff and Weiss as two techs working on characters in the unnamed fantasy park, with Weiss talking about taking something to Costa Rica. That something, as it turns out, is a dragon. But not just any dragon, as the wide shot reveals Drogon in all his glory, about to be butchered by Weiss for transport purposes.

Westworld showrunners Jonathan Nolan and Lisa Joy spoke to Variety about how the cameo came to be, with Nolan first noting how nice Benioff and Weiss were when they were trying to get Westworld off the ground:

“Those guys are the fucking nicest guys in the world. Usually when you come into a network where there’s a big dog show — and we’ve been in that position before — without naming names, there’s been [a vibe of], ‘We’re not inclined to be friendly to you if you’re the new kid on the block.’ We came to HBO with a big ambitious show at a point in which their show was and is the biggest fucking thing that’s ever been on TV. And they were so welcoming and so kind to us at a moment in which we were struggling through a first season and trying to figure out how it will work. We’ve remained friends.”

Nolan noted that Game of Thrones author George R.R. Martin has been pitching an official “Westerosworld” park in Westworld for years, while internally there’s been debate about adding a “Jurassic Park” world. This cameo, complete with Drogon and a nod to Costa Rica, brings those two ideas together as Nolan explained to IGN:

“Especially the Jurassic Park part of it, which we couldn’t resist. The argument there was all between whether or not one of the parks should be Westeros World, which George R.R. Martin has been pitching for years, and Dan and David—who are friends of ours and who we have joked about over the years [about] Jurassic Park, of course Crichton’s other theme park gone-wrong classic. And so we found a way to bring both of those great flavors together. We pitched to our friends Dan and Dave, whose show we dearly loved and really sort of blazed the trail for ambitious filmmaking on television. We pitched them this dumb idea, and they were kind enough to show up and play with us for a night. We bought them a beer afterwards, and it was an absolute pleasure having them on our set.”

As for bringing Drogon to life inside Westworld, Nolan and Joy revealed to Variety that they worked with Game of Thrones’ visual effects vendor Pixamundo to bring the official Thrones dragon to life—although there was debate over which version of Drogon to use, as Nolan explained:

“There was some back and forth about whether Season 4 or Season 5 Drogon, and some debate about how big the room was and what position the dragon could be in. But yeah, it’s just irresistible.”

Nolan and Joy aren’t yet revealing what this fantasy park is called, seemingly delighting in letting speculation run rampant over whether this is officially a Westerosworld or just a generic fantasy world. Either way, that reveal was a fun little treat.

For more on Westworld, check out our full recap of Season 3 Episode 2.