Dan Stevens (top) wants viewers of FX’s Legion to have more fun than his character is having.

In the new sci-fi drama that premieres Feb. 8 at 10 p.m. ET, Stevens plays David Haller, a young man who may have one of the greatest powers on earth and doesn’t know it.

Haller may have the power to move objects using only his mind. But all he knows for sure, after spending most of his life institutionalized, is that the medical world thinks he’s mentally ill.

That doesn’t mean they can fully explain the voices echoing through his head, the strange sounds and noises.

So David Haller’s life is a struggle, even when he finds a girlfriend, Syd Barrett (Rachel Keller, below left, with Stevens), who has been institutionalized for a different set of misguided reasons.

Still, Stevens doesn’t see Legion as entirely a dark drama.

“I think [creator] Noah Hawley wanted a show that could become a playground for writers and actors,” says Stevens.

Referring specifically to the casting of Bill Irwin (left) as Cary Loudermilk, a science geek, Stevens says, “That was right on the money. It was inspiring to have him around. He infused the set with a real sense of fun.”

The fun extends, Stevens suggests, to the staging and the whole look of Legion.

“The effects are extraordinary,” he says. “They’re as playful and silly and mischievous as the scripts. You have sets that look retro and would fit in your grandparents’ generation, yet there’s still future-vision going on.

“So you’re never quite sure where this thing is set, which is sort of liberating. It reminds me of the Black Panther comic, things taking on a timeless quality.”

It’s not exactly anything goes, but that’s the direction.  

“We had room for physical comedy, for dancing,” says Stevens. “We were creating a bit of mischief, really.”

He particularly enjoys the dancing part.

“For some reason, I’ve been called on to dance in several recent projects,” he says. “And of course that means dance lessons. Going to dance lessons together is an incredible way to get to know your costar.”

The costar connection is particularly critical here.

“David and Syd is the love story at the heart of Legion,” says Stevens. “We enjoy playing the idea of love as a madness.

“I think we’ve all found at some point that love is a kind of madness, and here we lay it on top of someone who’s already in this strange place.

“A straightforward boy/girl thing would not have been as interesting. David and Syd have to develop different ways of relating to each other.

“Their love is driven by David’s preoccupation with what’s inside his head – and she loves to navigate that. It gives the story complexity and depth.”

In fact, says Stevens, he doesn’t get all of Legion himself when he’s shooting it, or even when he sees it on the screen.

“When we watch playbacks, we see things that I swear we didn’t do in the shooting,” he says. “I’ve watched the pilot three times now and I saw things the third time that I hadn’t seen the first two. There are things that astound me – little Easter eggs here and there.”

The 34-year-old Stevens, who probably remains best known for his three seasons as Matthew Crawley in Downton Abbey, is fine if viewers take to the Internet to dissect each syllable of Legion, as Marvel and other comic book fans are prone to doing with shows they like. Or don’t like.

“There are elements we all aren’t sure about,” he says. “Like which of these things was reality? The show could be very enjoyable to fans on that level, and I’d love to read what people make of it.”

Adding another twist, the TV Legion starts from the comic characters and then charts its own course.

“We aren’t adapting specific comic storylines,” says Stevens. “But if you look at the original conception of Legion, the comic is really useful in terms of [David’s] manner, his mental state and his dry sense of humor.

“We didn’t want to get too invested in his having to be this or that. Strange things are happening to him and he hasn’t fully gotten to the point where he gets to in the comic.”

David Haller is still in largely uncharted waters, in other words, and doesn’t always seem to be moving toward land. But Stevens says he doesn’t find himself getting personally lost in it, for a very good reason.

“The real world is far, far weirder now,” he says, “than any Legion set.”