SPOILER ALERT: This article contains spoilers for the most recent episode of Westworld.

In the latest episode of Westworld, “The Winter Line,” a new medieval-themed park is revealed. Along with the park, some familiar faces appeared for Game of Thrones fans. The crossover happened when a group of park technicians waited to see if they would be laid off after working on their new Park, where they would be able to sword fight with knights and even the mighty dragon Drogon, one of the few surviving GoT characters. David Benioff and Dan Weiss, two of the showrunners of Game of Thrones, also appeared in the episode in brief cameos among the technicians.

This crossover event received longterm encouragement by GoT writer George RR Martin. The medieval park was originally slated to be called “Westerosworld,” according to Westworld co-showrunner Johnathan Nolan. Of Martin, Nolan had this to say, “We’re also friendly with George R.R. Martin, and George had consistently since the first season said, ‘We’ve got to do a tie-in with ‘Game of Thrones.” Nolan reminded Screenrant that “People forget that George was originally a TV writer and he came up in the TV world in which you’d occasionally have these crossover shows, which the fans would f—ing freak out over. So George had always been pitching the crossover show.”

He said the team had “wimped out” and decided to call it “Park 4” instead, leaving the in-universe inspiration for the park somewhat open ended. He went on to say that there was a medieval park in the Michael Crichton book of the same name that inspired Westworld the series, so the scene was to be a tribute to both the original book and GoT, the show he credits with paving the way for Westworld’s existence and success.

Westworld‘s next episode will air on HBO on Sunday, March 29.