Who Narrates “Sweet Tooth”? All About That Surprise Cameo in Season 3 (Exclusive)

Jim Mickle and executive producers Susan Downey and Amanda Burrell talk with PEOPLE about the big reveal of the narrator's identity in the season 3 finale

Sweet Tooth is adding one new face to the cast in season 3, but he's been a part of the show all along.

Set in a post-apocalyptic world where a mysterious disease has killed off most of the human population, the series based on Jeff Lemire’s comic books of the same name follows a young hybrid deer boy named Gus on a journey of self-discovery.

Throughout his adventures, as Gus comes in contact with a number of different people — including a retired football player named Tommy Jepperd, whom Gus nicknames Big Man, and a doctor named Aditya Singh — a mysterious narrator helps move the story along.

As the series comes to a close this season, many unresolved questions about the story are finally answered, including the identity of the narrator, voiced by actor James Brolin throughout the show.

Ahead of the series finale, PEOPLE spoke with showrunner Jim Mickle and executive producers Susan Downey and Amanda Burrell about the surprise narrator reveal and how they made it happen behind the scenes.

Here’s everything to know about that big cameo.

Warning: major spoilers for Sweet Tooth season 3 ahead. 

Related: James Brolin, 83, Says He Doesn't Plan on 'Stopping Work at Any Time' Ahead of Sweet Tooth Season 3 (Exclusive)

Who voices the narrator on Sweet Tooth?

Throughout the first three seasons, actor James Brolin has served as the show’s narrator. Speaking with PEOPLE exclusively, the actor reveals that it was executive producer Robert Downey Jr. who first requested him for the role.

“It was Robert Downey and [his wife] Susan who said, ‘We want Jim,’” Brolin explains. “I had lunch with him one day and within several weeks they called and said, ‘We want Jim only. Make a deal with him, Warner Brothers. Make a deal with him, Netflix.’”

“I thought that everything they seem to put their hands on has a really good chance,” he adds of why he decided to take on the narrator role.

Who is the narrator on Sweet Tooth?

In one of the final scenes, viewers learn that the narrator has actually been adult Gus this whole time: The narration from the first episode is repeated before the reveal.

Mickle notes that it was “always the plan” to have the narrator be adult Gus. “When we were getting the voiceover into episode 1 and sort of finding the role the narrator was going to play, I remember looking forward and going like, ‘Man, if it could connect to where it does in the comic book ... Who knows what'll happen years from now as we tell the story? But if it could, that would be quite great,’” he recalls. “We tried to pay attention to that as we went through, every time he speaks in the show for three seasons. It was hard to pull off, but I'm so glad that we did because it's so cool.”

He adds that watching actor Christian Convery (who plays Gus) recite the narration from the first episode was incredibly emotional to watch. “That was a big moment for me, because when we were shooting Christian telling that story, he was so composed and he was trying to make sure that he got that story right,” Mickle adds. “And when he did it, I broke down on set because I just flashed back to when we cast him and he was just an 8-year-old kid and he was just kind of a little goofball that happened to be good at this.”

“Watching that evolution of him from a little kid auditioning to somebody who at the end wanted to make sure that he nailed it so that he felt good and felt like he had done what he wanted to do with the character,” he continues. “You could just see that he was like, ‘I know that I'm going to walk away from this scene and want to know that I got it.’”

Does James Brolin appear in Sweet Tooth season 3?

For the big reveal of the narrator’s identity, Brolin makes a surprise cameo as adult Gus in the finale — antlers, flannel and all.

Downey credits her husband Robert for envisioning Brolin as adult Gus early on. “He just saw it from the jump,” she explains. “I don't even know that he consciously saw it relative to Christian, but it just ended up being one of those things that made so much sense.”

Burrell adds that they always “knew [Brolin’s] voice would be incredible” as the narrator but once they got to season 3, they knew they had to end the show with him on screen. “Bringing him to New Zealand and getting him in those antlers, it felt like he was really Gus, he'd really been on this journey with us. It was perfect.”

For Brolin, he says he was blown away when he first walked onto the set, noting that the sound stages were some of the “most extravagant” and had the most “gorgeous handiwork” he’s ever seen.

Though he didn’t share the screen with his younger counterpart Convery, Brolin reveals they did hit it off behind the scenes. “We got together right away,” Brolin says. “His mom is a hoot and very friendly, so he therefore is real gregarious and we did a lot of talking.”

He adds that he and the young actor felt a connection right away.

“When you are on a regular set with an actor for a while, you start to throw jokes back and forth and you feel nice and loose with him, and I got that immediately with him,” he notes. “[I don’t know if it was because] I watched the show and he knew who I was, [but] for some reason, he felt at ease with me too. I felt like I knew him for a long time.”

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