Emmy-nominated Harbour breaks down the 1999 "X-Files" episode "Field Trip," and why it still resonates. Plus: His favorite "Stranger Things" episode.

“Stranger Things” star David Harbour was a struggling twentysomething actor in New York in the late 1990s when he came across what would become his favorite TV episode of all time: “The X-Files” Season 6 installment “Field Trip.”

It’s an unconventional choice: One of the show’s classic “Monster of the Week” stories, this one was a bit different. Mulder and Scully are investigating the mysterious death of a couple, but it turns out the culprit was a giant fungal growth that causes hallucinations and ingests its victims. The two of them are soon trapped themselves, and experiencing their own weird hallucinations.

“So you’re being digested by the earth and you’re hallucinating your life,” Harbour said. “When I watched it I was in my 20s, I was really into that concept. We’re all being digested by the earth and we’re all just dreaming a life that has meaning and purpose while our bodies are being slowly eaten alive. That metaphor hit me really hard.”

Harbour, who’s Emmy-nominated for the second year in a row in the Outstanding Drama Supporting Actor category, sat down with IndieWire’s TURN IT ON podcast to discuss his favorite TV episode, and how its themes actually relate quite a bit to “Stranger Things.” Harbour also reveals his favorite episode of “Stranger Things” so far, and how the show is evolving as it heads into Season 3. Listen below!

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The 21st episode of “The X-Files” Season 6, “Field Trip” was written by Vince Gilligan and John Shiban, from a story by Frank Spotnitz, and directed by the late Kim Manners — all “X-Files” legends. You could tell, Harbour said: “It has a confident hand to it.”

Harbour said, like many “X-Files” fans, he fell in love with the dynamic between Mulder (David Duchovny) and Scully (Gillian Anderson) through the years. That pays off in the ability to suspend disbelief in an episode like “Field Trip.”

“It actually as a result of how invested you are in the relationships of the characters and how interesting the characters are and how much you love Mulder and Scully and their relationship, you forget about plot stuff that’s important and doesn’t quite make sense,” he said. “You just buy it and you’re cool with it. Whatever you want to do, if you want to have a mind meld between Mulder and Scully, sure!”

That’s why Harbour gravitated more toward the “Monster of the Week” episodes of “The X-Files,” rather than its mythology segments. That’s the opposite of what he likes to do as an actor — “I don’t want to do procedural, I want to do longform” — but “I want to see what happens when those two people get together.”

Harbour could have used more of a romance between the two, however: “I want to see them drive each other crazy. I know people love that tension but I need to learn how to be in relationships with people that you have complicated dynamics with.”

Comparing “Stranger Things” to “The X-Files,” he notes that his show shares some of the same tropes.

“I think ‘Stranger Things’ does this as well,” he says of letting some mysteries go unexplained. “The Upside Down being this thing that we haven’t quite defined and it still continues to grow and mutate. I don’t know if it has particular limits to it that we sort of use the upside-down as the story goes along.”

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But “Stranger Things” has also put its own spin on some classic sci-fi tropes, he added.

“The same tropes of everyone’s concerned something might be coming back to Hawkins, and Hopper’s like, ‘nah, I don’t think so,'” he said. “I mean! But the characters are developing and becoming more savvy.”

After the success of Season 1, Harbour said he was “worried” about the follow-up.

“But now that it worked, the world is so big. In terms of further seasons, I’m not as nervous. You have a fabric,” he said. “There’s a lot of stuff to mine.”

Harbour is pretty mum on Season 3, other than to note that it’s now 1985 and the kids are becoming teenagers.

“There’s so much about the ’80s that we are exploring on a subtle level, politically, social, culture-wise,” he said. “The ’80s moved themselves. The way film is developing during that time too. There’s so much fun to be had.”

As for how long “Stranger Things” will continue, especially as the show’s kids age, Harbour said, “I think we’re not going to overstay our welcome. We have a complete story that will wrap up.”

Also listen above to find out which “Stranger Things” episode Harbour chose as his favorite and why, and what to expect when his starring role in “Hellboy” comes to theaters next winter.

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IndieWire’s “TURN IT ON with Michael Schneider” is a weekly dive into what’s new and what’s now on TV — no matter what you’re watching or where you’re watching it. With an enormous amount of choices overwhelming even the most sophisticated viewer, “TURN IT ON” is a must-listen for TV fans looking to make sense of what to watch and where to watch it.

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