Once told by a spiritualist that the city would be important in his future, he achieved his big breakthrough at the Pavilion Theatre when, after the thinly attended first night of his first Mrs Brown play, with no advance bookings and disaster looming, huge audiences appeared for subsequent shows on the strength of word of mouth.
It set the whole ball rolling and O'Carroll has never looked back. His creation Agnes Brown - a recently bereaved Dublin mother-of-seven with a foul mouth and a heart of gold - has proved extraordinarily resonant.
A radio series spawned books, five plays, a film starring Anjelica Huston and a hugely popular TV series.
As Brian Beacom's affectionate biography, and O'Carroll's own contributions, make clear, Mrs Brown is largely based on his formidable mother, Maureen O'Carroll, a former novice nun who became a teacher, anti-poverty campaigner and activist for women's rights before being elected to the Irish parliament. There, she was the first female chief whip and shadow foreign minister. The youngest of her 11 children, Brendan was his mother's favourite, "the special one" who inherited much of her chutzpah and dynamism.
Battling dyslexia, beatings by the Christian Brothers and the temptations of petty crime, Brendan left school at 12 to work as a waiter. Left insolvent at 35 by the ruin of his pub business, which his co-owner stripped bare while he was on holiday, he embarked on a standup career. He was soon gigging with showbands in pubs, and when he blagged his way into producing some soap opera segments for a radio show, Agnes Brown and her unruly family were born.
The character and TV series has provoked mixed reactions, ranging from "postmodern and hilarious" to "dire". What has made it so contentious?
In the theatre O'Carroll is a life force. In Mrs Brown Rides Again in 2006 he had a packed Pavilion audience rocking with laughter, the loudest I had experienced in a theatre until One Man, Two Guvnors. But while O'Carroll's stream of put-downs and one-liners is brilliantly delivered and often very funny, the material sometimes has uncomfortable misogynistic overtones and the sexual politics were dated, with Mrs B's gay son Rory seeming to be straight out of the John Inman school of camp. Beacom does makes the point that including a gay character was a bold move at a time when homosexuality in Ireland was still illegal.
Surprisingly, given O'Carroll's warmth, what grates is not the character's profanity but the cloying sentimentality of the treatment. The possibility Beacom floats that, in comparison to past drag acts, Mrs B may be "reworking the old comic styles into something cutting edge and contemporary" is flattering to deceive: it is not cutting edge.
O'Carroll is clear the character's appeal is vested in Agnes as the sort of earthy matriarch everyone can identify with. He believes the reason it is a big hit in Glasgow and northern cities but not in Edinburgh or London is the character works best with working-class communities which have direct experience of the type of extended family it depicts.
Its success is also to do with O'Carroll's unconventional way of working - he tours a 20-strong company largely made up of family and friends - and to his promoting of his shows as "people's theatre" that exist outside the mainstream art theatre establishment. O'Carroll suggests he has an audience that doesn't normally go to theatres.
Judging from the Pavilion he is right, but the pantomime feel accentuates the fact that Mrs Brown is also tapping into an older tradition of working class popular theatre that has been largely forgotten.
Until the 1950s Glasgow had vibrant popular theatres such as the Queens and Metropole which, featuring comediennes like Dora Lindsay, Doris Droy and Grace Clark, offered entertainment rooted in the social and economic realities of life for working people. Wartime pantos presided over by "Suicide Sal" herself, Doris Droy, combined traditional fantasy with scenes set in tenements and health clinics, including risque routines about housewives trading sexual favours to settle tradesmen's bills.
These female performers are the homegrown antecedents of Mrs Brown and it would be good if theatre makers in the subsidised sector could find a way to reconnect with this wider popular audience.
As Beacom writes, O'Carroll's future looks stellar, with a new Mrs Brown film on the cards. Like his alter-ego, O'Carroll is anything but feckless.
l Dr Paul Maloney is an honorary research fellow in the School of Culture and Creative Arts at the University of Glasgow
The Real Mrs. Brown: Brendan O'Carroll - The Authorised Biography by Brian Beacom (Hodder & Stoughton Hardback, £20) is published on Thursday.