Midway through Donnie Darko, a creative young English teacher played by Drew Barrymore repeats the old maxim – recycled over the years by linguists, scholars and writers including JRR Tolkien – that the simple, banal phrase “cellar door” is the most purely, pleasingly harmonious combination of words in the English language. There’s something to be said for that, but one wonders if writer-director Richard Kelly was offering a challenge to the claim by naming his protagonist Donnie Darko – an irresistible, perfectly ridiculous name for an ordinary suburban schoolboy that nonetheless encapsulates his fey, eccentric aura. His new girlfriend says the name aloud, lolling it like a mint in her mouth, before observing that it makes him sound like “some kind of superhero”. “What makes you think I’m not?” he replies, deadpan. Well, what indeed. Kelly’s sci-fi-tinted tale of adolescent isolation came out six months before Spider-Man, the film that kick-started the now all-consuming superhero movie revival, and the two have more in common than you might initially assume: both are stories of an awkward teenage boy coming to terms with what appear to be otherworldly abilities, and assuming responsibility for the world around them. For plucky Peter Parker, that means standard-issue feats of derring-do and defeating evil; for downcast Donnie Darko, it means ending and altering the very timeline in which he exists, ultimately dying so that others may live. As superhero origin stories go, it doesn’t have much franchise potential: Donnie’s legend begins and ends in one fell swoop. But it has an eerie, enduring power: would that many comic-book heroes’ stories were so noble and haunting and finite. A 20th anniversary is an odd one for Donnie Darko to celebrate: if any film should be granted eternal teenagedom, Kelly’s vastly ambitious debut feature is it. I first saw it when I was 19 or so, which was pretty much ideal. The film, with its blend of ordinary high-school angst and trippy, whoa-what-was-THAT philosophy was pretty much designed to be shared among teenagers like a secret – a work that both understands their view of the world and offers to expand it in cosmic, confusing ways. That quality was enhanced by the bitty slow burn of its release. Following mixed reviews from its Sundance premiere, the film went unclaimed by a distributor for several months. Released into a handful of US cinemas in October 2001 – in the bleak shadow of 9/11, particularly unfortunate timing given its inciting incident of airborne misfortune – the film didn’t exactly find an audience, grossing only half a million dollars by the end of its run. Its cult, instead, was born of home video and DVD, which in turn prompted renewed life in cinemas: by the time it made it to the UK, a full year after its US release, the film had built enough cachet to become an indie box office hit and hipster object of fascination. (A street-art exhibition was dedicated to it at the Shoreditch bar Dream Bags Jaguar Shoes, which is about the most early-2000s measure of fashionability you could ask for.) By the time its key soundtrack cut – a mournful cover of Tears For Fears’ Mad World by swiftly forgotten singer-songwriter Gary Jules and the film’s composer Michael Andrews – topped the next year’s UK Christmas top 40, its pop phenomenon status was assured. The release of a director’s cut the next year kept the word-of-mouth cycle going for a film that was, by then, on every other university student’s list of all-time favourites. This all feels an awfully long time ago: revisiting the film in my late 30s, I was concerned that Donnie Darko, itself a Reagan-era period piece, would now play as a quaint time capsule of my millennial youth, reflecting my own then-callow ideas about time, space and society. Yet give or take some visual effects that were always on the resourcefully ropey end, the film stands up beautifully. A decades-on coat of nostalgia now only enhances its prevailing sense of sadness, its sorrow for lives curtailed and misunderstood by the superficially functional American suburbia represented by Patrick Swayze’s devilish motivational speaker and Beth Grant’s Christian-fundamentalist harpy. They’re caricatures, of course: the film saves its nuance for its outcasts. As sensitively written by Kelly and exquisitely performed by Jake Gyllenhaal – then gawky and goth-eyed, at odds with his lanky body, eons away from the dreamboat he’d become – the reluctantly therapied, heavily medicated Donnie now plays as a prescient touchstone for a later generation of mental health awareness. In the wake of the Columbine tragedy, American indie cinema was awash with tortured young men on the brink of something dreadful, yet Donnie’s sense of separation from others is neither romanticised nor made unduly sinister: the film’s solemnly soulful adventures in time travel offer a kind of symbolic validation for anyone who sees, feels or experiences the world differently from everyone around them. It’s not exactly a comforting expression of solidarity – as you choose to see it, the film is bittersweet at best, and plungingly tragic at worst – but it feels honest and inclusive in its despair. Would that most teen dramas, to say nothing of most superhero movies, had quite so much weighing on them.