With a movie in the pipeline, millions of viewers, a BAFTA award and sell-out stadium tours, Mrs Brown's Boys seems an unstoppable force.
There is a Romanian Mrs Brown, a Slovenian Mrs Brown, an Icelandic Mrs Brown, and she is due to appear as a Turkish woman.
She's the hottest thing on our telly boxes, but Mrs Brown wasn't always so popular with TV bosses. O'Carroll (57) had to fight to gain a spot on primetime TV.
The youngest of 11 children, Brendan was born in Finglas in 1995. When he was growing up, this mother Maureen was a well-known Labour Party RD.
She told him he could do whatever he wanted if he put his mind to it. As a result, he became known as the 'can-do kid'. And that attitude seems to have stuck with him throughout his career.
Brendan left school at 12 and worked as a waiter, disco manager, milkman, pirate radio DJ and decorator before creating Mrs Brown. He stumbled into comedy after a brief stint as a publican in Finglas in the 1980s.
The character of Agnes is loosely based on Finglas housewife Annie Browne. Annie was the mother of Brendan's early writing partner Gerard Browne.
Agnes first hit the airwaves in 1992 on 2FM. Mrs Browne kept listeners entertained with her foul-mouthed ramblings for two weeks.
But RTE decided not to give Brendan and Mrs Brown a more permanent slot.
There was uncertainty whether O'Carroll's brand of humour would travel outside his home base.
But Brendan was able to gain a national profile as a result of an appearance on the Late Late Show in 1993.
O'Carroll was interviewed Gay Byrne, and says Gaybo was the man who "discovered him".
After the appearance Brendan wrote several best-selling novels.
He thinks he knows why his work appeals: "I think that we've discovered a forgotten audience -- an audience that comedy forgot," he says.
"There's no Dick Emery anymore, there's no Les Dawson, and we're filling that gap."
Despite finding his audience, Brendan was left with debts of over €1.5m in the late 1990s after he ploughed his own money into Sparrow's Trap, a movie about a failed boxer which never made it to the screen.
"I started to feel invincible and to think I was bullet proof, so I wrote a movie screenplay about a young Irish boxer, I thought I could walk on water."
MCD owner Denis Desmond approached O'Carroll and told him he had a free night in the Olympia Theatre every Tuesday. And so Brendan made his return to stage doing stand-up -- and has maintained a close link with the Olympia since.
Two years later, he had a sold-out Mrs Browne In Mourning on stage at the Gaiety.
"I was broke and I had no gigs. But the owner of the Gaiety Theatre in Dublin asked me to write a show, so I wrote a play based on Mrs Brown. It broke box-office records over here and Mrs Brown saved my bacon," he recalled.
In 2000, Brendan wrote the screen adaptation of The Mammy -- Agnes Brown -- based on his book that he wrote in 1994. He appeared in the feature film alongside actress Anjelica Huston -- who also directed the movie.
But Irish TV executives were still slow to see the potential of Mrs Brown. It wasn't until a BBC executive happened to attend an O'Carroll gig that Mrs Brown moved from the stage to our TV sets.
"We took the show to Liverpool and Glasgow and BBC producer Stephen McCrum walked into my dressing room, and asked if I'd be interested in developing it for a sitcom."
When Mrs Brown's Boys first aired on the BBC in March 2011, it was met with scathing criticism from the UK and Irish press.
With its slapstick asides delivered directly to camera, its shoddy costumes changes and double entendres, it's not entirely surprising that the critics don't like it.
But the all-important viewers disagree -- and it has proved to be a massive success.
The series is set for even more success this year with two festive specials. And Brendan is predicted to net over €10m from royalties from repeats this year.
While Brendan is the first to admit his family enjoy the financial benefits of all things Mrs Brown, charity remains close to his heart.
This Christmas, more than 1,500 families in the Dublin area will enjoy a full turkey and ham dinner after he decided to donate a substantial number of vouchers to St Vincent de Paul.
Next year, Brendan will start shooting a Mrs Brown's Boys feature film.
"I haven't written it yet," said the comic. "That's what success does: they give you money and say 'whatever you think', so I took the money."
And he will be taking the Mrs Brown Stage Show around Australia in 2014 where tickets are expected to sell out.
"We've been number one in Australia for weeks and even beat their top TV show, Australia's Got Talent," said Rory Cowen, who plays Rory Brown.