All week the Irish have spoken of their enduring rivalry with England, who they meet on Saturday at Twickenham.
Stephen Ferris accused the English of being "bad losers", while Rory Best and Rob Kearney have argued that Ireland's dominance of the fixture since 2004 is purely because they are a superior team.
Kearney also admitted his surprise that Stuart Lancaster's side defeated France in Paris last weekend.
And O'Callaghan, who toured with the Lions in 2005 and 2009, claims that facing England awakens the competitive spirit like no other opposition.
"I wouldn't say I'm friendly with any of their players, but I've been on Lions tours with them," the 32-year-old said.
"The biggest thing I've taken away those tours is that you can build up a perception of people before you actually get to know to them.
"I remember going on Lions tours believing half these fellas are eejits (idiots) and that I wouldn't like them, only to come away thinking they're the soundest guys you could meet.
"That's definitely been the case, but come Saturday they'll be in an England shirt and nothing will change in the way we treat them.
"England shirts are a red rag to the Irish. When we play England in anything, we want to do well and perform.
"Maybe it goes back to Euro 88 (the Republic of Ireland beat England 1-0) or something like that - you tend to remember great days of Irish results against England teams.
"It lifts the place and secures bragging rights for a while.
"Sometimes you don't like to be the small nation so when you play England it's a chance to show them up."
Ireland have amassed an outstanding record against England, winning seven of the last eight meetings in the Six Nations and triumphing on three of their last four visits to Twickenham.
The only blemish was the 33-10 drubbing in London in 2008, a defeat that concluded Eddie O'Sullivan's reign as head coach.
The victory in last year's Six Nations was sweeter than most after a swaggering England were denied the Grand Slam with a 24-8 hiding at Lansdowne Road.
Ireland were seething at what they perceived to be a dismissive attitude from the visitors and responded with a performance of rare ferocity.
Revenge was exacted five months later, however, when Martin Johnson's team dominated the World Cup warm-up match at Aviva Stadium 20-9.
O'Callaghan, who will be winning his 85th cap on Saturday, insists the fear factor of facing England has long since been replaced by an expectation of success.
"In the past Irish teams went to Twickenham and were thumped, coming away with their tails between their legs," the Munster lock said.
"Now we travel to England with our provinces and the national team and get results.
"We're getting these results on the back of getting the process right.
"When we do that we win, when we don't do that we get what we did in the World Cup warm-up game, which is being handed our arses.
"It's disappointing to say it but we played a friendly that day and they played a Test match. We were caught short because of that.
"That's what you get when you don't perform the physical side of it and Saturday's game will come down to how the pack performs.
"It's up to the pack because when we perform we get great days like the Shane Horgan try in 2006."
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