Forget Kryptonite, comic-book heroes face an even greater threat: overfamiliarity. Audiences fatigued by the recurring sight of lunchbox-ready masked crimefighters are hungry for something different. That’s why psychological thriller Jessica Jones was a breakout hit for Netflix, why the exuberant Lego Batman has the edge over Ben Affleck’s glum Dark Knight, and why Logan – an elegiac outlier set in its own sequel-resistant, dead-end timeline – has been hymned as the greatest superhero movie ever made. The profane, violent Logan was following in the irreverent footsteps of Deadpool, a movie that disrupted the multiplex by plucking a character from the X-Men’s mutant mythos and tailoring a movie to his unique talents rather than servicing the wider franchise.

Legion has achieved something similar on TV. It focuses on The X-Men’s institutionalised character David Haller (played with dazed intensity by Downton Abbey’s Dan Stevens, sporting a series of scruffy haircuts). So far, critics seem to be impressed: the New York Times called it a “trippy tour de force”, while Rolling Stone compared it favourably to the unique cinematic visions of Kubrick. Wes Anderson might also see something rather familiar in the pop-art cocktail of bold colours, retro styling and symmetrical compositions that make Legion the most visually arresting and aesthetically decadent show currently on TV.

Legion review – Marvel takes on mental illness in dazzling new show Read more

In the original X-Men comics, Haller was the estranged son of mega-mutant Charles Xavier but Legion has so far downplayed any familial connections. The true nature of Haller’s psychological problems also seem rather vague: his hallucinations could be mistaken for the manifestation of uncanny powers, or vice versa. So Legion is an arms-length addition to the X-franchise, and showrunner Noah Hawley, who spent three years developing the project, seems to be making the most of his additional wriggle-room.

Although Hawley is best known for Fargo, his award-winning anthology TV series, the key to understanding his authorial approach might be another of his pet projects, a long-gestating TV adaptation of Kurt Vonnegut’s acerbic satire Cat’s Cradle. Certainly, Legion’s time-hopping story structure, pop-art vibe and enthusiasm for formal experimentation feel more of a piece with Slaughterhouse-Five than, say, the Fantastic Four.

Jean Smart has witnessed Hawley and his creative approach up close, having collaborated with him on the second series of Fargo, where she starred as the brittle, calculating head of a 1970s crime clan. They bonded over a love of music. “Noah says he always wanted to be a rock’n’roller,” she says, “but he doesn’t like staying up late so it never worked out.”

Facebook Twitter Pinterest Legion: (from left) Aubrey Plaza as Lenny “Cornflakes” Busker, Rachel Keller as Syd Barrett and Dan Stevens as David Haller. Photograph: Michelle Faye/FX

In Legion, Smart plays Melanie Bird, another self-possessed matriarchal figure, operating a sanctuary for mutants on a remote horse farm. After she masterminds Haller’s prison break from the ominous Clockworks psychiatric facility, she encourages him to engage directly with his volatile memories. “I think she feels very protective of David,” says Smart, “but I think she is concerned that he is something of a loose cannon, or even a loose atom bomb.” A handy machine called a Memory Cube allows Bird and her acolytes to burrow directly into Haller’s fractured consciousness, zig-zagging Inception-style through some of his most traumatic memories.

With such a deliberately scrambled narrative, Hawley was presumably the one person who could visualise how all the scattered pieces of Legion were supposed to fit together. Like David, he was walking around with an entire alternate reality in his head. Did Smart see any telling parallels between the showrunner and his lead character? “I’m sure that there’s a lot of Noah in David,” she says. “Noah really is a Renaissance man. He knows every genre of film, he knows every genre of music, so he sort of cherry-picks the things that he finds the most fascinating, attractive and romantic.”

Facebook Twitter Pinterest Legion showrunner Noah Hawley. Photograph: Maarten de Boer/Getty

The original X-Men were conceived by Stan Lee and Jack Kirby in 1963 as heroes who protected humanity even as they faced discrimination and fear because of their uncanny powers. Over the decades, that metaphor has been fluid enough to mirror racial and sexual prejudice and Legion applies it to mental illness. “That was something that fascinated me about this show from the get-go,” says Smart. “I think it talks to how we treat people with mental illness, Noah wanted it to be very sympathetic. Hopefully we’re a lot more knowledgable and open-minded about it these days.” Superhero fiction has long been about escapism – fuelling fantasies of strength, or being able to fly away – but that seems to be increasingly matched by an interest in empathy. Legion explores the downsides of being exceptional. As David’s girlfriend Sydney Barrett, a mutant whose physical touch can trigger a Vice Versa-style body swap, laments: “Who teaches us to be normal when we’re one of a kind?”

Unlike other TV shows based on comic books, Legion seems more interested in cult pop culture than making callbacks to the comics. There are Bollywood-style dance sequences soundtracked by Serge Gainsbourg and a (deeply unsettling) rendition of Kermit the Frog’s banjo-powered anthem Rainbow Connection. Stylistically, also, it is almost aggressively different, having more in common with the clinically precise dread of Black Mirror than the quasi-realistic, Kevlar-heavy worlds of Arrow or The Flash. Legion’s heightened, fever-dream atmosphere even invites comparisons to the biggest TV cult of all: Twin Peaks.

Facebook Twitter Pinterest The X factor: Legion stars Dan Stevens and Rachel Keller. Photograph: Michelle Faye/FX

Coincidentally or not, the show also seems to chime with a very contemporary notion of 2017 as an exhausting, ongoing battle with a constantly shifting, unreliable reality. “Ever since 9/11, in a way, we’ve all had this level of anxiety and fear that has never completely gone away,” says Smart. “Certainly in the US right now we are all feeling incredible stress about what’s happening and wondering what the future holds. We are all looking for someone who can ride in on a white horse and get rid of the bad guys. I think people find that aspect of Legion very appealing.”

Legion may have the mutant ability to warp, reshape and re-energise superhero TV tropes but, while it has been well reviewed, the ratings are not yet stellar. Thankfully a second season has been confirmed, just as the season one finale looms. And, rather refreshingly, there has been no heart-sinking sense of characters being shuffled around a larger board to be optimally positioned to launch the next movie, TV series or opportunistic spin-off. Smart suggests we strap in tight. “I think the ending will be completely unexpected,” she says. “Up until the very last minute of episode eight you will not see what’s coming.”

Legion is on Thursday 30 March, 9pm, Fox