It’s been a while since we’ve seen Jacob Anderson on screen. The last time the actor was on television, it was in season 8 of Game of Thrones, playing Daenerys Targaryen’s loyal captain Grey Worm. And now he’s making a return to TV with a recurring role in Doctor Who season 13.

Now, we aren’t quite sure what to expect from Anderson’s character in Doctor Who. He’s not technically a companion of the Doctor; those roles are filled by Mandip Gill as Yaz and newcomer John Bishop as Dan. But he will be more than a one-episode character.

Speaking to Digital Spy and other media, the actor compared working on Doctor Who and Game of Thrones. For one thing, he’s already an old hand at keeping secrets. "I’m very used to it. Now, when anyone sends me an NDA and they’re like, ‘Are you going to be alright to keep secrets?’ I’m like, ‘Come on!’ Yeah, I’m very used to it. I only ever consider things if there’s a massive element of secrecy to it."

So that sounds like that’s a "no" to him revealing anything big about his mysterious character in Doctor Who.

Anderson also spoke about the differences between the Doctor Who and Game of Thrones fandoms. And Thrones fans, be advised, you might not like what you read next:

"I’m looking forward to [Doctor Who], and I’m sure [the fans] are better. I can say that, right? Because Game of Thrones is finished. I love meeting people that are passionate about something. I love good storytelling, and I’m passionate about it. I get excited.

"I’m a nerd, so when I meet fellow nerds, and they’re excited to meet you because you’ve been a part of something they care about, how nice is that? I don’t want to play them off against each other."

Jodie Whittaker names her favorite Doctor Who guest star

Anderson won’t be the only guest on Doctor Who this season—and he's far from the only one who’s appeared on the show over the years. If you're wondering which guest has been Jodie Whittaker's favorite during her run on the show, the Doctor Who star said it was Stephen Fry, who, she explained, has "the most extraordinary brain."

Fry appeared in the previous season of Doctor Who during the Spyfall arc. Whittaker said that she was a bit nervous to meet him again, considering the last time they acted together, in 2007's St Trinian's, her character was "questionable." As she explained, "I offered him some pills or something, which is highly inappropriate."

Doctor Who season 13 premieres on October 31.