"He just appeared at my doorway and I couldn't believe it,'' teacher Jenny Donald said.
The 21-year-old player was born in Australia, but lived in Auckland for five years as a child and went to Rutherford Primary School.
On a day off from training, O'Connor had time with his mother to visit his old Te Atatu stomping ground.
The star player tweeted his reminiscence to his fans as he made his way through his old neighbourhood.
"Still same owners at the corner dairy _ Fav fish n chip shop still standing tall! But Skate parks gone, had some fond memories there!'' he wrote.
The next stop was his old primary school to visit his favourite teacher, Mrs Donald, who had no idea he was coming.
She said she could not have been more pleased about her surprise and even "teared up'' a bit.
"I knew who it was immediately and he gave me a big hug. Then his mum told me, `You know what? You were one of his favourite teachers _ he'd remembered all that time since he was about 7 or 8,'' she told the Herald.
"I thought he'd be flat out when he was here but he said he had the day off today, so it was really nice of him to come and visit _ it was really cool.''
Mrs Donald taught the Wallaby in Year 3 and his two brothers also went through her classroom and she grew quite close to their mother before the family moved to Australia when O'Connor was 11.
Before he played for the Wallabies, he was eligible to be selected for all three Tri-Nations teams, because though he is Australian by birth, his mother is from South Africa and his father is from New Zealand.
Mrs Donald said yesterday's visit was a little awkward because her class had been studying the Rugby World Cup so her room was "decked out in black''.
"Then one of the Wallabies shows up, and the room's covered in All Blacks.''
The teacher said she had a word to O'Connor about missing the announcement of the Wallabies' squad for the cup because he had over-slept after a big night the day before - meaning he was dropped from the team for the last Tri-Nations match against the All Blacks. He returned to the squad as a reserve for the Wallabies' opening World Cup match against Italy.
"I gave him a little bit of a ribbing about that and his mum said it wouldn't happen again. Then we had a little bit of a giggle, because that's what boys that age do.''
Mrs Donald said the "littlies'' she teaches mostly did not recognise O'Connor, but some of them had seen him on television.
"All the kids thought he looked like Justin Bieber because of his haircut ... One of the boys said he was the one who kicked with Quade Cooper.''
Mrs Donald said she was an avid All Blacks supporter but had followed O'Connor's career.
"I talk to a lot of people about him who are usually very shocked to hear that I taught him.''
After leaving Rutherford Primary, O'Connor and his mother went to visit his old church, then went to catch up with the school's former lunch lady, who had boys of a similar to the player and his brothers.
"Jst met few kids from my old school Rutherford now off to my Church, where my Dad was a Minister for 5 years Te Atatu Baptist.''
O'Connor then ended his trip down memory lane at the Te Atatu Rugby League Club.
"Lunch with some old family friends then had a walk on the field where it all started. Tat Roosters!''
- Amelia Wade, The New Zealand Herald