"The amount of Irish people that travelled out and also those backpacking around. it really meant an awful lot to us."
Both O'Callaghan and Ronan O'Gara will now have a chance to readjust to family life back home before linking up with Munster towards the end of the month.
Indeed, O'Gara's eldest children, twins Molly and Rua, were thrilled to see their dad as he arrived home on the day of their third birthday.
"They're looking forward to their presents now! I didn't want to be home for their birthday really, but we'll take this as the next best thing," admitted O'Gara, with reference to the fact that professionally he would rather be back in New Zealand preparing for a World Cup semi-final.
"It's a long way home and it was a disappointing finish for us, but that's the way it goes at this level. They're a great bunch of lads and there's a lot of highlights to take away from the competition."
O'Gara, who is now a veteran of three World Cups, was again asked about his future with the Ireland team. During the tournament in New Zealand he had to clarify comments he made in a post-match TV interview when he said that he will 'be done with Ireland in a few weeks'.
Speaking today, he said: "I haven't thought about long term. An awful lot happens in a week. Irish rugby's been so good to me and you don't walk away from that. You see what's in store.
"Then the other side of it is that I'm 34 and there's new talent coming through. We'll see what happens, but you don't ever turn your back on a great country."
In the past two months O'Gara has made five starts for Ireland, including three against Russia, Italy and Wales at the World Cup.
He also kicked the match-winning penalties in the historic victory over Australia, and his assured place-kicking in recent weeks has pushed his Irish points-scoring record to 1075 points.
It is clear that he has been energised by Ireland's achievement of finishing top of a World Cup pool for the first time, although the quarter-final defeat to Wales was tough to take for all involved.
The positive feelings surrounding Ireland's Kiwi adventure will help when the Wellington loss is mulled over in in the coming days. O'Gara will certainly have happier memories of New Zealand 2011 compared to the side's exit from the last World Cup in France.
He added: "I remember coming back home four years ago and the feeling was completely different. Yet, the next runout we got at Musgrave Park when we played for Munster was something we'll never forget.
"Irish people are really loyal people. The team are hurting. It's disappointing but there's been some great highlights along the way, as I said, and you don't forget them either."