Mrs Brown's Boys' Brendan O'Carroll on the danger of being overexposed

Brendan O'Carroll as his alter ego Agnes Brown.

Eight years ago, top BBC producer Stephen McCrum was invited to go from London to Glasgow to watch a little-known stage show called Mrs Brown's Boys – in which the Irish performer Brendan O'Carroll plays the foul-mouthed matriarch of a chaotic Dublin family.

The moment McCrum saw it, he immediately realised that it could be a hit on television.

O'Carroll recalls that, "After the show, Stephen came back to the dressing room and said, 'We'd like to make a sitcom of this'.

Mrs Brown with chat show guest Sue Perkins.

"I went, 'Thanks very much'.

"When he had gone, I said I had no idea who he was. 'He's probably a janitor,' I said."

The cast and guests film an episode of All Round To Mrs Brown's.

Since that moment in 2009, Mrs Brown's Boys has become a global phenomenon.

It has spawned three series, 12 specials, many more live shows and even a movie.

Now, O'Carroll, 61, has produced a spin-off show, All Round To Mrs Brown's, in which the indomitable Dubliner welcomes into her house a host of celebrities, including Pamela Anderson, Judy Murray, James Blunt, Sue Perkins, Peter Andre, Holly Willoughby, Philip Schofield, Lulu and The Kaiser Chiefs.

This spoof chat show, now screening on TVNZ 1, has given O'Carroll yet another roaring success and it has already been commissioned for a second series.

The Mrs Brown ensemble has always been a family affair.

O'Carroll's real-life wife portrays his TV daughter, his actual daughter plays his TV son's wife, and his older sister takes the role of his neighbour and best friend.

The show has struck such a chord because audiences are drawn to the fundamentally warm family unit at the heart of the sitcom.

They also enjoy the sheer anarchy that prevails at Agnes Brown's.

As O'Carroll puts it, "We are not the Waltons, that's for sure".

In the UK, Mrs Brown's Boys and its talk-show spin-off regularly pull in audiences of up to eight million people. O'Carroll says he finds that figure hard to take in.

"You don't really get a sense of what eight million people watching feels like. It is twice the population of Ireland, so I can't even get a concept of that."

The Dubliner has also been taken aback by the sheer affection that has been directed at his show.

"We kind of know it is funny," he says. "We've been doing this on the stage for a while, so we know there are gags that are going to work.

"But I'm really surprised about how much people love the show. I've never felt that way about any programme in my life."

For all its popularity, however, the Mrs Brown shows have still been subject to some sniffy reviews. But O'Carroll remains gloriously unaffected by any negative critiques.

"I don't know one reviewer yet who has stopped people going to a show or has made a show successful. It is down to the audience. Audiences seem to vote with their feet and not with what they read."

O'Carroll reveals that sometimes the cast and he just "sit down and giggle" about the show's tremendous global profile.

However, he is well aware of the dangers of being overexposed.

"Mrs Brown has become a really strong brand and we do not want to throw it away.

"I don't care how funny you think you are, people are entitled to think, 'Oh no, not him again'."

The show's creator asserts that the cast will never get complacent about its enormous success.

"I think it is because we all had real jobs," he reflects. "Bugsy (O'Neill, who plays Grandad Brown) was a window washer, Pepsi (Shields, who plays Mark, Mrs Brown's oldest child) was a mechanic, Rory (Cowan, who plays Rory, Mrs Brown's third son) worked in EMI for many years, Jenny (Gibney, who plays Cathy, Mrs Brown's only daughter) worked in a bank, Eilish (who plays Winnie, Mrs Brown's neighbour and best friend) worked for Guinness, I was a waiter – everybody had real jobs."

O'Carroll concludes that, "You are always terrified that one day they will find out you are a waiter and will want their money back. So I think we do appreciate it more than normal."

Rory moves out 

Mrs Brown's Boys star Rory Cowan has announced that he is leaving the show, after 26 years performing with the cast.

The actor, who plays Agnes Brown's son Rory, said he felt "it was time to go". His last performance with the comedy troupe was at London's 02 Arena on July 9.

"I hadn't been happy working for the Mrs Brown's Boys company for the last 18 months to two years," Rory told the Irish Daily Mail, adding that he wouldn't share any further details.

"I did the final show, packed my stuff into a small Waitrose plastic bag and I just left the venue."