South by South West attendees have no doubt noticed a strong 'Game of Thrones' presence at the festival this year. Pedicabs and buses are plastered with advertisements for the show and the 'HBO: The Escape' exhibit at 800 Congress features a 'Game of Thrones' themed escape room and photo ops with the Iron Throne.

'Game of Thrones' pedicab at SXSW

But the real prize for fans came on Sunday when showrunners David Benioff and DB Weiss took to the stage to discuss the show. And in case a panel with Benioff and Weiss wasn't cool enough, stars Maisie Williams and Sophie Turner were the moderators.

Ahead of the panel, 'Game of Thrones' fans were told to go to 'HBO: The Escape' for a surprise at noon.

Those lucky enough to make in time were greeted by Williams and Turner, who play the Stark sisters, Arya and Sansa.

Maisie Williams and Sophie Tucker arrive at 'HBO: The Escape'

Afterward, those present at their arrival were asked to sign waivers to appear on 'Carpool Karaoke,' so it's likely that we'll soon see an episode of the show featuring the Stark sisters.

A few hours later, the group kicked off the panel by discussing the show's casting. Benioff and Weiss said that Williams' role was particularly difficult to cast, she was chosen out of 300 girls. Turner was one of three final contenders for the role. The two landed the parts after they had a "chemistry reading" together and it became clear that the duo would play great sisters.

It is very clear that Williams and Turner are close in life. In fact, during the panel, they pointed out their matching tattoos, which show the date that they were told they landed the roles on 'Game of Thrones.'

Weiss and Benioff mentioned how well Williams and Turner have handled the great success of the show and subsequent notoriety they've received.

"You could have easily become Biebers and you didn't," Weiss joked.

As for the easiest character to cast, Benioff and Weiss said that the decision to cast Peter Dinklage as Tyrion Lannister and Mark Addy as Robert Baratheon were the first and easiest for them to make.

Interestingly, the actress who played Catelyn Stark had to be recast after the pilot, which caused some of the scenes to be re-shot with Michelle Fairley.

"When we wrapped on the pilot, we didn't know if it would get picked up or not," Benioff told the crowd. He recalled Williams and Turner crying together on the set of Winterfell after they finished shooting the pilot and assuring the girls that the pilot would get picked up and they would continue shooting.

"I was lying," he said. "I didn't know."

When asked about what draws people to their characters, the showrunners focused on Arya and Sansa.

"People are drawn to rebels," Benioff said of Arya. He goes on to say that although Sansa is often an annoying, stuck-up teenager, she ends up with "one of the most interesting journeys."

"Sansa has to face hard choices," Benioff said.

As any 'Game of Thrones' fan knows, no character is safe from death. Benioff and Weiss discussed the difficulty of killing off so many great characters.

"Killing (Jason) Momoa sucked," Weiss said. "We never totally recovered from getting rid of him."

On the subject of Jason Momoa, who played Khal Drogo, Benioff shared the story of when Momoa broke his hand while playing the 'slap game.'

Benioff said he was playing a game in which he held out his hands, palms up, and Momoa would slap both hands. The game ended up abruptly when Momoa accidentally "squished" Benioff's hand.

"Don't play the slap game with Jason Momoa," he warned. Sage advice.

The group shared stories of behind-the-scenes pranks the showrunners would play on cast members. One time, they said, they wrote a fake scene for Kit Harington, Jon Snow, and told him the scene would have "his face melted off" and burn off his hair.

"He bought it until we started laughing," Weiss said.

The only cast member to prank them back was Nikolaj Coster-Waldau, who plays Jaimie Lannister. Benioff and Weiss said that he once sent them a picture of himself with his head shaved only two weeks before they were scheduled to start shooting. Apparently, it was such a big deal that HBO lawyers were talking to his agent before they realized it was a joke.

Several musicians have appeared on the show in the past including band members from Sigur Ros and Mastadon. The showrunners revealed on Sunday that Ed Sheeran will make an appearance in the upcoming season. They said that they had him on the show because Williams is a fan.

When Turner asked when Justin Bieber will make an appearance, they promised season nine. Unfortunately for Turner and other Beliebers, the show will end with season eight.

An audience member asked the group about the importance 'Game of Thrones' has had on the portrayal of women in television.

Weiss pointed out that in the books, there are many "competent females characters who have agency," and aren't secondary to male characters.

"It was an actress-centric show before we even started, just from the source material," Weiss explained.

Turner said that one of her proudest moments of working on the show came after the episode of her wedding night with Ramsay Bolton aired.

"[The scene] led to discussion about the taboo of rape and turned me into kind of an activist," Turner said.

Although the premiere date for the seventh season was just announced last week, the showrunners seem to have already decided the length of the eighth and final season. Benioff told the audience Sunday that the final season will only contain six episodes.

"From the beginning, we've wanted to tell a 70-hour movie. It will turn out to be a 73-hour movie, but it's stayed relatively the same of having the beginning, middle and now we're coming to the end," Benioff said.

When asked what shows they would like to write for other than 'Game of Thrones,' Benioff said 'Rick and Morty' and Weiss said 'Atlanta.' Both admitted, however, that they would not do well writing for either show.

Weiss and Benioff said that once 'Game of Thrones' is over they will move on, but likely continue writing together. They said there may be spin-off shows based on surviving characters of the series (so someone will survive) but, if so, they won't have any part in it.