EXCLUSIVE: Justin Theroux's Satisfying Return to (and Departure From) TV

"I was very satisfied with the way we closed the show," Justin Theroux tells ET, referring to the upcoming series finale of HBO's The Leftovers. After two critically acclaimed seasons and a Peabody Award, the show adapted from Tom Perrotta's novel of the same name will air its final eight episodes starting Sunday, April 16.

A suburban character drama set off by a departure of 2 percent of the world's population, the show explores the lives of those still on Earth as they grapple with what it means to be left behind. For Kevin Garvey Jr. (Theroux), that means trying to maintain some semblance normalcy as it becomes clear that he is far from it. From his visions in season one to coming back to life in season two, Kevin is grappling with the idea he may be something more in season three. Is he the second coming of Jesus Christ? "Certain people think he's Jesus, but Kevin doesn't think he's Jesus," Theroux says of the scruffy cop, who in season three follows girlfriend Nora Durst (Carrie Coon) to Melbourne, Australia, as the anniversary of the "Sudden Departure" looms heavily on the show's characters.

Given what happens in the first seven episodes that were provided to the press, it seems that the show will answer that question -- or bring audiences closer to an answer. (However, Lindelof has said that The Leftovers would not answer all the questions asked on the series.) But Theroux isn't offering any spoilers on that front. "It felt like there was a real piece of punctuation at the end of all the characters," he says, though he certainly wants audiences to enjoy it. "If you roll with it, it'll be a more satisfying experience."

MORE: Why Justin Theroux Won't Take Any Credit for 'The Leftovers'

One thing he does make clear about season three is that there'll be no headline-generating moments about his body like the bulging jogging scene or his bathtub nudity. "Hopefully they will be talking about the quality of the show and how wonderfully written and acted it is," Theroux says with a laugh, adding that he didn't see either of those moments becoming the headline fodder they did.

"That was certainly not intentional. It was, I guess, a happy accident. Justin is a man who is endowed with great talent," Lindelof says of the season one moment that even left co-star Liv Tyler distracted. ("I'm like, '[I] can't help but look there,'" she revealed on Watch What Happens Live With Andy Cohen.)

But Lindelof offers praise of more than Theroux's physical appeal, adding that he is a fearless actor. "He kept delivering every time we'd write these crazy things for him to do," he continues. "So that would inspire us as writers to say, 'There's really nothing this man can't do. It was almost a fun challenge, like, 'How do we keep him uncomfortable?'"

For Theroux, The Leftovers was his first full-time return to TV nearly 15 years after a season on CBS' Washington, D.C., cop drama, The District -- and a satisfying experience at that. He was hesitant about joining another show with 22 episodes per season and the exhaustion that comes from it ("That can just crush you"), but The Leftovers -- only 28 episodes in total -- offered a reprieve from that previous experience. "When it gets longer than that, it starts to feel tired," he says. And after tip-toeing his way back onto TV with recurring parts on the HBO series Six Feet Under and John Adams, and Parks and Recreation on NBC, he was inclined to give himself full-time to The Leftovers.

"It was everything I hoped it would be," Theroux says of his time with the HBO series. As an actor, he was pushed to improve his range, adding that Lindelof never allowed him the opportunity to "phone it in." And given that the series moved production from New York to Austin, Texas, and then to Australia, the actor never felt dormant. Not only was his character constantly moving forward, but he was physically going there with him. By the time it came to the final episode, which was shot down under, he and the cast were trying to squeeze every moment of enjoyment out of it, adding: "We were just sort of embracing it and really trying to serve Damon and Tom."

MORE: 'The Leftovers' Star Kevin Carroll Isn't Ready to Let Go Ahead of Final Season

And it seems, as an actor, that's the most important thing Theroux can do: serve the writing. "My job is just to sing whatever notes they write me," he says. But he didn't just sing, he belted, putting his full body into the performance, most notably in the season two episode "International Assassin," which not only earned Theroux Emmy buzz but headlines for his onscreen injuries.

Waking up naked in a hotel bathtub, Kevin is quickly transformed into a James Bond-like character as he fights with a bellhop. The sequence itself resulted in a few injuries -- just some of the many Theroux's suffered filming the series -- that shut down production. "They used that take," he says of the scene where the attacker puts a gun to Kevin's head, resulting in a broken nose and 10 stitches for the actor. "The crew was ecstatic, because we wrapped [shooting] at a nice, reasonable hour for everyone to go to the bar. They were all toasting me that Friday night."

Season three resulted in one trip to the emergency room, but aside from the elements of Australia's Outback ("It was very uncomfortable, a lot"), Theroux didn't offer any stories of serious injuries except that he doesn't warn wife Jennifer Aniston of his repeated mishaps. "I don't tell her until I'm out of the hospital."

In fact, he couldn't reveal much during FaceTime sessions with Aniston, who herself is a fan of the show and avoided spoilers about the new season. "She's like, 'Don't tell me anything," Theroux says, explaining that he was just trying to catch up with his wife, who did not travel to Australia during the filming of the final episodes. "I'm just talking about my life right now… but she's like, 'If it spoils the show, I don't want to know about it.' So I'll say, 'Well, I'm in a very wet place, it's cold and I'm being submerged.'" Though that's a moment fans won't see until later in the season.

With filming complete and promotion of the series nearly over (the finale airs June 4), Theroux is starting to map out the rest of his year. While there's no formal plan -- "The mandate for people I work with is just find really good material," he says -- the actor is focusing on his other talent as a screenwriter.

In addition to his onscreen work, he's written screenplays for Iron Man 2, Rock of Ages, Tropic Thunder and Zoolander 2. His latest writing assignments include the long-awaited Space Invaders, as well as the Will Ferrell comedy Swear to God, which he's also slated to direct. "I have a few things that I've actually already written that I'm tweaking and retooling," he says, adding that he has another screenplay he wants to add to his growing list of projects.

And while he has his eye out for roles for himself, what tends to happen is what Theroux calls a bad habit of writing parts for other people. "I don't really write for myself, necessarily," he says. When asked if he would ever write something for Aniston, who has said that if she was going to return to TV, it would be on a premium cable show, the actor says definitely. "If the right thing came around… We toss around ideas occasionally, but it's got to be something I want to write and something she wants to act in, which is harder than you might think. But yeah, it would be fantastic if we were able to do something together."

--Additional reporting by Leanne Aguilera

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