YOU’LL very much enjoy My Old School, the fizzing documentary of the Brandon Lee story. A 32-year-old dropout, Brian MacKinnon, turns up at his old school, Bearsden Academy. He pretends to be 17 and Canadian-Scots, adopting the Lee name.

Why do something so odd? MacKinnon’s aim is to get back into medical school, which then – in the early 1990s – wouldn’t accept candidates over 30. So he pretends to be a teenager again in order to get the grades.

The movie uses Daria-style animation, a chorus of old schoolmates and Alan Cumming lip-syncing to an audio interview with MacKinnon. They’ve exuberantly captured the jaw-dropping nature of the story.

But, particularly on my second viewing, I found it moving as well as amusing. There is something genuinely untethered and challenging about Brian MacKinnon/Brandon Lee, which the director laces through the jolliness. Most challenging of all? Perhaps we are not so far from MacKinnon’s strategic deceptions as we might imagine.

For one thing, MacKinnon deploys a range of New Age and self-help techniques that are surely not unknown among the perjink salons of bourgeois-professional Bearsden. He believes that “active dreaming” – a learnable technique where you consciously direct your nighttime imaginings – has the power to make things concretely real.

When MacKinnon traumatically flunks his first year at Glasgow University medical school, back at his actual age of 17, he notes that his active dreaming (of being a doctor) ceases. But MacKinnon also states at one point that “as an active dreamer, there are things you can do to keep yourself young”. What would they be?

He sounds sincere in his belief that he is “literally telepathic” with his beloved mum. MacKinnon also holds that he used hypnotic techniques (“mind control”) to persuade teachers that they didn’t need to see his birth certificate. And he seems proud of his ability to fool people with “Russian accents, American accents … whatever it takes”.

His self-belief, even when his deceptions are fully revealed, is undimmed at the documentary’s end. “I’m strong, bright, sharp and I still have a lot to offer – maybe I can make a difference”, he says in a public interview, his head now shaven like a monk’s. (He’s already told us he had an IQ of 162 at nine-years-old). MacKinnon’s final line is dauntless: “I still get visions of possible futures – because I still have tricks up my sleeve”.

His strangest expression of all, for me, is when MacKinnon tries to explain why he’s still relentlessly applying to get a medical degree, at various institutions round the world: “I wanna know that I know what I know.”

But isn’t this the guy who believes his mind has a range of reality-bending near-superpowers? Doesn’t he know what he wants to know? There is something tragic about MacKinnon’s epistemological angst here. It’s as if his medical degree will be the anchor for someone who wilfully slips in and out of truth.

But it looks like it’s unattainable (and, as a few of his classmates concede, how would you feel if this guy turned up as your doctor?). MacKinnon will never know that he knows what he knows, in the officially approved sense.

However, “Brandon Lee” knows something that is an imperishable and ultra-modern truth: a powerful story makes its own reality. “When you have an adversary,” says MacKinnon, “the thing you wanna do, if you wanna prevail, is to do something unimaginable, that’s so out there that people would never dream you would do that.”

It’s no doubt helpful that MacKinnon saw the schoolkids around him “as just ciphers to me … It wasn’t what I was focusing on”.

This profound fictiveness inside MacKinnon explains the weirdness of seeing him hit the TV couches, after his first exposure in the early 90s. He calmly explains his deception to goggle-eyed hosts: this was merely a canny strategy, something to beat the med-school rules.

BUT this is more mesmerism, active dreaming, trickery up his sleeve. We heard at the Everyman screening in Glasgow that MacKinnon is working with another production company to make a new sitcom out of the whole affair.

And even his decision to only give an audio interview to the makers of My Old School, requiring Cumming’s lip-synch performance, is a classic Brandon Lee move. You work with his version and tailoring of reality, not yours.

Indeed, this may be the era that Lee/MacKinnon has been waiting for. Our disenchanted fantasia – fake news, deep fakes, “reality” TV, “feels over reals”, memes and stunts – where PR and comms saturate and frame everything that moves.

My Old School is estimable for the way it keeps striking philosophical and ethical grace notes, which make the laughter darker and more disturbing. I was struck throughout the film by the gentle testimony of Stefen, a black classmate of MacKinnon’s. Suffering tedious 90s racism, Stefen was taken under Brandon Lee’s wing, benefitting from study and social time with him. Stefen is very clear that without Lee’s help – yes, conducted in fully faked Canadian character – he wouldn’t have become a qualified pharmacist.

Yet Stefen is asked a killer question at the end: Do you think Brandon Lee was a person? His answer is head-spinning. “All I can say is: what is a person?”

Well, indeed. On second viewing, something “icky” appears (the word is used to describe Lee’s lingering kiss with his 16-year-old co-star in the school performance of South Pacific).

The chorus of classmates, who bear giggling and sneering witness to MacKinnon’s deception, are themselves playing a shadow game. In the first half of the movie, they relate MacKinnon’s biographical fictions as if they believe them – the director evidently semi-scripting them to help his movie process the tale.

In the second half, they flip into their own incredulous responses to it all – as if the first half of diegesis hadn’t happened. In a movie about a grand liar, it makes them all look like cheap tricks. We only find out towards the end, in a reverse shot, that one of the pupils who’s been telling the story, Jono, is actually the documentary maker.

So how far can we even believe this cut of MacKinnon’s story? Is it bullshitters wall-to-wall?

But as Stefen’s answer implies, there is maybe as much truth to be found in the kindness of actions, than in the integrity or coherence of the person enacting them. We seem to have established some facts about MacKinnon’s biography. His dad – not a university professor, as “Brandon Lee” claimed, but a local lollipop man – gave MacKinnon a death-bed benediction: that his life would indeed have meaning.

This super-bright fantasist – for whom “medicine was the tide, there was never going to be anything else” – then decided to actively realise his dream … by doing “something unimaginable”.

“You can follow your dreams without deceiving people,” says one of his more unctuous classmates. Forgive me: I work in a realm – and when answering my question at the Everyman, so does the director Jono McLeod – where personas and avatars, trimmed and polished biographies, and fake-it-till-you-make-it are an accepted norm.

The test is more about compassion than veracity. Who gets hurt by an embroidering, softening or illusion of the truth? And in a society and economy geared toward performance and self-promotion, how many stones can we throw at MacKinnon/Lee, from our own glass houses?

Go to see My Old School for the cheek and exuberance of aspirational Glaswegians. But linger in your seat about its deeper message, intentional or not. To charge someone with fakery, in these weird and wired days, is a tough call.

For information on how to see My Old School, visit dogwoof.com/my-old-school