"There was so much emotion. It's unbelievable and fairy tale stuff, really, that's hard to get to grips with," Mr Carbery said.
"You can imagine the excitement. Joseph (his grandson) was born in Auckland and moved to Dargaville before he was 1, and they then moved to Ireland when he was 10 (with dad Joey and mum Amanda, who is from the Irish town of Athy).
"But like any kid growing up in New Zealand, he dreamed of playing for the All Blacks.
"He's a New Zealand-type number 10 and it's ironic that he's gone from wanting to be an All Black to being part of Ireland's historic win against them.
"Amazing really, and to think he did it with Jared Payne, too, another Northland connection."
Mr Carbery said the perfect continuation of his fairy tale script would be for him to be chosen in the British and Irish Lions to tour NZ next year. Payne could also be in the Lions' side.
"We don't want to get too far ahead of things. But wouldn't it be wonderful if he played for the Lions in his old province of Northland at Toll Stadium (the first match of the Lions' tour)?" Mr Carbery said.
Mr Carbery said Joey was first spotted by NZ rugby coaching great Sir Graham Henry, who was helping out with coaching at Leinster last year.
"Sir Graham was helping out with coaching the coaches there and saw Joseph playing, and said to them 'there's your number 10 for the next 10 years.' Now that's some accolade coming from Graham Henry."
The Irish Times caught up with Joey Carbery after the game.
"Yeah, it was a bit crazy but I didn't really think about that, I went back to basics and did what I normally do," he told the Irish Times.
"Aw, crazy. I can't believe it. It's unbelievable."
The All Blacks were his boyhood heroes growing up in Dargaville.
"It was always mixed between the two, I had the jerseys of both. I would have grown up with Mils Muliaina and Dan Carter being there, but also O'Gara and O'Driscoll as well," Joey Carbery told the Irish Times.
And after the match, Aaron Cruden gave him a real ABs jersey and told him to keep his Irish jersey as it was his debut.
Northland Rugby Union acting chief executive Ali McGinn said it was good to see players who learned their craft in Northland performing on the international stage, even if it was for another country.
"Just like a number of the top coaches internationally around the world are from New Zealand, there seems to be a growing number of Kiwis of European descent starting to appear more and more in international teams," Mr McGinn said.
He said it would be good if Carbery and Payne both earned a place in the Lions team to play at Toll Stadium next June.
"After (Sunday's) result the Irish players will have the inside running ahead of some of the other (Lions') countries," he said.
Joey Carbery's first teacher, as a 5-year-old at Dargaville's St Joseph's School, was Anne
Lugtigheid (then Heappey) who remembers him as a diligent, popular student, who was "just a really nice kid".
"He was was bright and one of those ideal children to teach - sporty, academic and really popular. He was a real sweetheart who always tried really hard," Mrs Lugtigheid said.
She watched the game on Sunday morning and thought Joey did well when he came on.
