By now you're all familiar with the narrative arc: talented little wicketkeeper from South Dunedin gets picked for higher honours too soon, struggles to realise his obvious talent, gives up the gloves, becomes an attacking if inconsistent batsman, gains the captaincy in controversial circumstances, morphs into a cricketing statesman.
Even the arc of McCullum the man is well-versed: cheeky little chappie, loves a beer and durry, a punt and a late night, before settling down as a family- and businessman.
It's an interesting sketch but consists of outlines only. He's often portrayed in cartoonish terms - a cricketing Popeye, all forearms and bravado - but his is a more complex, tangled picture.
And it's a picture a lot of people just don't get, which is why he invokes, still, such bile from his critics (case in point: the reaction to New Zealand's loss to Australia at the Basin Reserve and his rapid decline as a test-match batsman).
As he prepares to step away from public life, we'll take a stroll through it.
That quote is indisputably true. Born in Dunedin and raised in the southern suburbs, McCullum has always had blue-collar sensibilities.
He was a dressing room urchin at the Albion Club at Culling Park, St Kilda. His father, Stu, was a dashing left-hand opening bat who played 75 first-class matches for Otago and his return of two centuries and an average of 24.4 was generally considered to have sold his talent short.
But that era was an exciting one for Otago cricket. It was a team of strong, innovative personalities, from Glenn Turner to Warren Lees, Carl Dickel and John Cushen. And, most of all, convenor of selectors, Ray Hunt.
A keen observer of that period of southern dominance was Richard Boock, who is in the unique position of having seen the very young McCullum (Boock's older brother Stephen played for Otago and New Zealand); reported on his ascension to national colours as cricket writer for the Herald; and now shares the same employer at New Zealand Cricket.
"My first memories of Brendon were at Molyneux Park, Alexandra," says Boock. "He, Nathan, Warren's kid Greg and a bunch of others would be there constantly, just hitting balls around and playing from start to finish."
Nathan McCullum remembers those days like yesterday.
"We'd follow Dad down to Albion on a Tuesday and Thursday night, hanging out the back waiting for someone to hit us some catches. We'd join in the fielding with the older guys."
As soon as he and brother Nathan - 13 months his senior - were old enough, they were playing, and fighting. The McCullum sibling relationship could best be described as competitive.
"Boys always have a few dust-ups, don't they," Nathan recalls. "There was a bit of rough and tumble, a fair bit of sulking but nothing too serious."
Brendon might have seemed preternaturally talented, but Nathan says that is selling his brother short.
"People drop that word 'talent' like it was something that was dealt to you, but for Brendon it was hours and hours of playing with mates at the school, at home, at the park. Cricket, golf, basketball, soccer, you name it. We'd play for hours on end.
"It was practice without us realising it."
McCullum's precocious ability was obvious from the moment he walked through the gates of King's High School and that, Nathan says, was the precursor to the greatest piece of luck to befall his younger brother.
"He was fortunate enough to make the 1st XI as a third former. That was the start of him testing himself against bigger and better opposition. It was the best thing that happened to him.
"If any kid was to get that chance, I'd say take it."
At the time the 1st XI was coached by John Cushen, a hyper-aggressive fast bowler for Auckland and Otago in his day.
"It was working-class families down there," Cushen said in a Cricket Monthly profile on McCullum. "The ones whose parents couldn't afford to send their kids to the Billy Ibadulla coaching schools. When I'd take Otago U16 and 18 teams, it was all John McGlashan College and Otago Boys' High kids. There weren't many boys from King's."
Cushen identified McCullum as a rare wicketkeeping talent and rang Stu to ask if he minded picking his boy as a third-former, a rare honour. Dad gave his blessing and the young McCullum and Cushen began an enduring mentorship that turned into friendship.
"He batted down at nine or 10, but he had a great attitude," Cushen recalled. "I remember, once we were playing Southland Boys' High and it was a close game, but we got down to our last wicket and needed 16 runs off the final over to win.
"In those days, the thinking was, if you can't win, then you don't bloody lose. I sent out the call to see off the last over. Baz was going, 'I can do this. I can do it.' I said, 'No, you won't.' He listened, but that was him to a tee. Even at that age there was nothing he didn't think he couldn't do."
McCullum's schoolboy sporting career is nothing short of stellar. While he shone at cricket he was also a brilliant rugby player, famously keeping Daniel Carter on the bench for South Island schools.
South Dunedin was also where McCullum's other great love was forged. Growing up in the shadow of Forbury Park, McCullum developed a love for the racing industry that lasts to this day.
Rugby, racing and Speight's might be classic Southern Man stereotype, but it was his cricket ability that was about to thrust him into the spotlight.
Brendon McCullum wasn't ready when he was picked to open the batting for New Zealand in 2002. The national selectors were about the only people in the country who didn't know that a one-day tri-series in Australia involving the home team and South Africa was not the right place to blood a 20-year-old with a handful of first-class games behind him.
"I remember talking to Dayle Hadlee who was running the academy at the time," says Boock. "He told me Brendon would be the biggest thing we ever had. 'I've just seen him do some outrageous things with the bat,' he said. He was right, but it just took him a while to get there."
Even looking at his team mugshot seems instructive now: a callow, almost naïve kid trying to look hard.
He repaid the selectors for their impetuosity with scores of 5 (run out by partner Mark Richardson), 37, a third-ball duck and 29. In the home series against England that followed he mustered 9, 5 and 7. He was dropped.
He made the squad for the Cricket World Cup in South Africa in 2003. McCullum got his first taste of controversy there, being one of a number of players evicted from a Durban nightclub shortly before Chris Cairns was king hit. His was a name that would continue to figure largely in McCullum's life.
Those that followed the team in those days remember a kid who was a follower in every sense, eager to please the senior members of the side - too eager to please in many ways. This was a team of over-sized personalities and big egos and McCullum was all too happy to trail along in their slipstream, go one-for-one with the party boys at the bar, hoping to get the odd pat on the back on the way.
"He was young and impressionable," says Boock, who was by then covering the national team with the Herald. "He was soaking up everything. He was popular and senior guys liked to take him along with them."
McCullum could be flighty, certainly with the bat and also with the gloves, where he was superbly athletic and had great hands, but would blend spectacular catches with the odd inexplicable miss.
He wasn't helped, either, by a curious period in New Zealand cricket's curious history. With John Bracewell in charge it appeared McCullum was the accidental answer to every problem the team had.
"He was the sticking plaster for every wound the team had," Boock says.
If there was a guilelessness about the way he sometimes played, it could easily be attributed to the fact "he was never allowed to settle down", Boock believes.
The early McCullum was a classic case of New Zealand's shallow talent pool throwing up a youngster who you knew could play a bit, but was still working out who he was as a person, yet alone a cricketer.
Towards the end of Bracewell's reign, however, senior players including Nathan Astle and Craig McMillan departed and suddenly McCullum was a senior player, a leader rather than follower.
Great is such a subjective word.
Just look at Alexander. The young Macedonian won a few battles and forged an empire, yet his army still mutinied, he ended up dead at 32 and suffered the further indignity of being played by Colin Farrell in a biopic.
Great, or reckless?
Now, there are three words to divide New Zealand's cricket populace when it comes to Brendon McCullum.
"He's complex. He's got contradictory skills. He's mercurial and you'll see both sides of that package in the same innings," says Boock. "He's a fantastic player who everyone wonders if he could have been even better if he'd just done things more their way.
"If you were lucky enough to see him in full cry, it was more memorable than many of the so-called greats."
In terms of purity of glovework, he would probably sit slightly behind Ian Smith and Adam Parore, though he was arguably more athletic than both. However, his batting would be more than enough to vault him above those two into any neutral selector's all-time New Zealand XI.
Again, does that qualify as great, or highlight a weak field?
What many people forget is that McCullum played 48 one-day internationals (ODIs) before he made his test debut. What many people also forget is he played most of them poorly, particularly with the bat. When he made his test debut his ODI average stood at 20.04, a pitiful reflection of his talent. His ODI stats have never really righted. He averages much the same as a keeper-batsman as he does a batsman. He averages much the same in the top three as he did lower in the order.
Even accounting for the fact that his explosive opening batsmanship was pivotal in New Zealand's 2015 Cricket World Cup run, and that his strike rate has allowed the likes of Martin Guptill and Kane Williamson to flourish without the burden of scoreboard pressure, there is no way you can describe his ODI career as anything other than an under-achievement.
T20s are different. McCullum was a T20 pioneer and, as the format achieves universal recognition as a valid part of the game, will go down as one of the early greats, like Viv Richards in ODIs. His scene-setting 158 not out for Kolkata Knight Riders in the very first Indian Premier League match in 2008 and two international centuries - particularly the 116 not out against Australia at Lancaster Park in 2010 - were early markers to the possibilities the format offere; his execution of shots like the scoop and the slash almost uncanny.
Tests, however, are most pundit's marker for greatness and it's also where McCullum's playing credentials are toughest to measure.
Even if he bags a pair in Christchurch, and he looks so out of touch it's entirely possible, he will finish with an average of 37.6, near enough the same as John Wright who most people regard as a New Zealand great; and Wright didn't spend half his career wicketkeeping or batting No 7 or lower.
He will almost certainly finish with 11 test centuries, bettered only by Wright (12), Kane Williamson (13), Ross Taylor (13) and Martin Crowe (17). Only Stephen Fleming (46) has more than McCullum's 31 half-centuries and only Fleming (7172) has more than McCullum's 6283 and, slowly, counting. No New Zealander has passed 200 more than his four assaults on this total.
There's the small matter of his 302 in Wellington, part of an epic 2014 where he became the first New Zealander to score 1000 runs in a calendar year.
Oh, and nobody anywhere has played 101 tests in a row from debut.
The less he's thought about his place in the firmament, the better he has become.
"I spent too much time worrying about numbers when I was younger, but then I realised stats can tell you what you want to hear," McCullum said recently. "I enjoy following other people's statistics, like Kane and Ross', more than mine.
"What I'm most proud of is that I've learnt from my mistakes. I've changed from a keeper-batsman to a batsman and I've got better."
Until this last, protracted and slightly painful year, this is undoubtedly true.
Does it qualify him as great? By world standards, probably not, by New Zealand standards almost certainly.
"There are some players," Boock says, "like former England captain Mike Brearley, whose whole was greater than their sum of parts. Brendon falls into that category.
"He is a better player than Brearley - a much more dynamic player, but like him his captaincy will define him."
"There are two captains in our cricket history who gave New Zealand a sense of independence - Geoff Howarth and McCullum."
Towards the end of 2014, a secret sect of Herald nabobs gathered around a small table to choose their New Zealander of the year.
By the time the white smoke appeared they had been unable to separate two acts of courage: Mary Quin, who testified at the trial of fundamentalist cleric Abu Hamza al-Masri; and Brendon McCullum, who would testify against his former mate and hero Chris Cairns at last year's match-fixing trial in London. Cairns was vindicated, acquitted of perjury. McCullum's motivations were challenged by critics. The length of time it took him to report allegations that Cairns approached him about getting involved in fixing (about three years) was probed. It was suggested that coming forward was part of a strategy to enhance 'Brand McCullum'.
"It was obviously a pretty big deal but it's time to move on," he said in the aftermath of the trial. "From my point of view I'm very happy with the evidence I gave in London but it's now time to move on.
"For me it wasn't about whether someone was guilty or not guilty - my role was to give evidence and I remained pretty unemotional about it."
The intriguing, perhaps even sad, wash-up from the whole imbroglio was that opinion of McCullum's involvement in the trial faithfully mirrored some people's perception of him as a cricketer and person. Some of the attacks on him were deeply personal.
While he retained a sense of detachment, others couldn't. To some he was stepping into a murky world and trying to make cricket a better place. To his critics he was sullying the game with reckless accusations.
As McCullum thinks of nothing but the next and last five days of his black-capped career, others will be left to ponder one of sport's most over-used words: legacy. McCullum, 34, will leave one and, as Boock points out, you won't just see it in New Zealand.
"His approach has touched a lot of people. You can see it in Eoin Morgan and Alastair Cook [England's ODI and test captains]," he says.
You will see it in Kane Williamson, too, New Zealand's captain-in-waiting.
McCullum's detractors - which sounds more and more like a disenfranchised Facebook group - will point to the way he took the reins from Ross Taylor in acrimonious circumstances; his failure in the World Cup final; and his habit of coming up small against Australia as evidence that his influence is overstated. But none of those who played with him and few that played against him will agree.
Corey Anderson said the 2015 World Cup squad would have "walked into fire" for him and thousands of previously disengaged fans reconnected to the summer game as the Black Caps retooled after the fiasco of the way McCullum replaced Taylor as captain and subsequent humiliation - 45 all out - at the hands of South Africa.
The secret to the revival was actually a painful self-examination of sorts: McCullum, coach Mike Hesson and manager Mike Sandle came to the inescapable conclusion that the public of New Zealand saw the team as puffed up and "overpaid prima donnas". Sure, they had to get better at batting, bowling and fielding, but just as importantly they had to get better as humans.
"Most of it emanated from us being semi-embarrassed about the way we had played in the past," McCullum would say. "It has to be authentic and it may not last - you can't force it down people's throats - but this is the way I want this team to play and I know the senior guys have similar feelings on it."
It was a top-down approach. There'd be little big-noting, no on-field confrontation (they hadn't earned the right to sledge), 100 per cent commitment and pride in the field. They knew they weren't good enough to win all the time, but they wanted to be a lot harder to beat.
The transformation was immediately obvious, though not necessarily through results. After 10 tests with McCullum in charge, the ledger stood at six draws and four losses, but something happened in the 10th match that signalled a spiritual as well as cricketing revival.
Taylor scored a double-ton, McCullum scored a ton after a long time between drinks and the two of them batted for a long time together. They shared a hug. It might not have been much, it might even be overstated, but there was suddenly a sense that although they might not be candidates to write the forewords to each other's biographies, they could co-exist and thrive together in the same team.
That kick-started a period of success unparalleled in New Zealand's less than stellar test cricketing history. There was the 2-0 home victory against the West Indies, where Taylor went on a run spree, followed by a 1-0 series victory against India, fortified by McCullum's ground-breaking triple century.
That was followed by a 2-1 series win in the West Indies, set up by Williamson's prodigious run-making, and a 1-1 drawn series against Pakistan in the UAE. The latter might just have been McCullum's finest hour. Rallying troops that didn't want to play after the death of Phil Hughes, McCullum scored 202 off just 188 balls and shared a 297-run partnership with Williamson.
"What you saw was a team playing without feeling," McCullum says. "What we learnt was that when you play without any of the pressures and expectations we normally put on ourselves, your skills can be properly expressed."
That was followed by a 2-0 home series win against Sri Lanka, where McCullum played his last great knock, 195 off 134 balls as test cricket returned to Christchurch for the first time since the devastating 2011 earthquake.
A series was drawn 1-1 in England (who would later that summer defeat Australia to regain the Ashes), before the anticipated twin series against Australia.
That hasn't gone so well, even accounting for the 2-0 series win against Sri Lanka in between.
Australia have outplayed the Black Caps. What's more, McCullum's on-field captaincy has looked muddled and his batting tired and ineffective.
But as he acknowledged after the defeat at the Basin: "Sometimes the game doesn't marry up to the ambitions you have."
Does he have one last shot to fire, or will he hand his critics' further ammunition for the firing squad?
That's the thing about McCullum, you see, you just never know...