The pair rowed themselves into Irish sporting history by winning the lightweight double sculls.
They pipped Germany and Italy to claim victory.
When asked post-race if there was any difficulty gelling since they became teammates, McCarthy said: “Not really, Paul is an absolute animal so it was handy enough to just sit behind him and try and emulate that.”
McCarthy's comments were echoed by the duo's rivals in the 2,000m lightweight double sculls, who were all in awe of the Irish pair and the standards they set.
“They are incredible,” said Jiri Simanek, who led Czech Republic to a fourth-place finish, their boat crossing the line 10 seconds behind the Irish and an agonising tenth of a second away from the medals. “We are in good shape but they are something out of space for us. They deserve it. Paul is a monster.”
His team-mate Miroslav Vrastil struck a similar tone. “Yeah, he is a monster,” he added. “We are in very good shape, but they are just better.”
Pietro Ruta, who helped Italy to bronze, said the Irish duo stand alone in their event. “It is such a strong crew,” he said. “They have a different strategy, they are very constant over the race but the last part, it’s good for them.”
The win is Ireland’s first Olympic gold medal in rowing and only the third ever in the sport.
Taoiseach Micheál Martin paid tribute to his fellow Cork men.
“I think it’s a tremendous day to celebrate. It really has stuck home to hearts and lifted the Irish people— and had the chance to speak to Paul’s father Teddy this morning. I know many, many of the people who looked after them over the years and coached them," he said.
“I pay tribute young athletes because the way they carry themselves I think speaks volumes for their families, their communities, and where they spring from.
“I think there’s great dignity in the way they behave in victory, and I think it's to their credit, and we're very proud of their, of their achievements. We look forward to some more high moments at the Olympics.”
O’Donovan and his brother Gary won the silver in the same event five years ago in Rio while the women’s four scooped a bronze in Tokyo yesterday.
For the first time in nine years the tricolour was raised highest at an Olympic medal ceremony after the pair were presented with their Olympic gold medals.
Earlier, O’Donovan and McCarthy clasped hands after crossing the finish line in 6.06.43, half a boat length ahead of the German crew who made life difficult for the Irish throughout a fascinating final. The underdogs laid down their challenge right from the gun, taking an early lead with Ireland and Italy disputing second.
In the opening 500m Germans Jonathan Rommelmann and Jason Osborne were ten lengths clear but the Irish crew’s strategy has always been based around upping the pace between the 500m and 1500m mark. As expected, Ireland began to close the gap and between the 1k and 1500m mark and they reduced the deficit until the boats were level.
It was now a two-crew race for gold with the pairs disputing the lead as the crews approached the grandstand. But O’Donovan and McCarthy had the strength and the speed to move ahead when it mattered most and as they approached the finish line they were a half a length in front.
It was the way the pair would want to have created history – a real race in which they were pushed to their limits but prevailed. Italy claimed the bronze medals.
Newly crowned Olympic champion O’Donovan said the gold medal race on the Sea Forest Waterway panned out much as the Irish crew had anticipated.
“The Germans and the Italians always have the quick start, you can be sure of that, and for once then we had a good start. It hadn’t been for the lack of effort (until now).
“The rest of the time we weren’t going off fast, so it was a bit of a surprise when we did and we weren’t totally dropped in the first 500 metres. Then we just put the heads down and ploughed on.”
“Fintan (McCarthy, his partner in the boat) said a few things to me during the race but you would be on auto pilot half the time,” insisted the double Olympic medallist.
He insisted there was never any sense the race was getting away from them, even though the Germans led until the 1500m mark.
“I don’t think there was any moment of panic. We were kind happy out with our position, like. We often have a big sprint at the end if we need it. So, we knew if we were sitting level or even a bit behind, we could pull something off. We were eking out a bit of a finish before the end so that was good.”
McCarthy, who watched O’Donovan and his brother Gary win a silver medal in Rio five years from the local pub in Skibbereen, was surprised at how nerveless he felt before the biggest six-and-a -half minutes of his sporting career.
“I would usually get a bit nervous, but I felt ready. It was good.”
His immediate post-race celebrations had to be curtailed when he had to go to doping control. “That brings you right back down to earth,” he said.
The duo dedicate their win to hard work, but when asked if there is more to it than just hard work, O’Donovan said: “It depends how far deep you want to go into things, there’s boats and there’s coaches and support staff.
“We’ve a good boat anyway and the best coach Dominic Casey so we can’t complain with that either.
“And there’s the mother at home and the father and the grandmother and all the support they’d be giving us all throughout the years.
“And you need so much luck, like that we were born in the place that we were born and there was a rowing club nearby and myself and Gary got a bit of luck going to Rio and we were lucky that Fintan was there watching and was in the rowing club and trained really hard and then made it into the boat.
“So, all of those things together but fundamentally we did an awful lot of training, and that’s the main ingredient.”
Asked about how the win felt compared to his Rio silver which he achieved with his brother Gary, O’Donovan said he didn’t think too much about it.
“I mean, to be honest, that was five years ago. I rowed with the brother, I didn’t think too much about how I felt at the time, compared to how I’m feeling now.
“After winning gold medal here today, and a silver medal last time, I probably am a little hit happier because, as a kid, you’re dreaming of winning a gold medal. A silver medal is nice, but Fintan did the right job, straight to the top in his first Games so he must be pretty happy too.”
McCarthy said he was proud to bringing home the gold medal.
“It’s really satisfying to have done it. Great to make everyone at home proud and put Ireland in the history books.”
O’Donovan said he doesn’t care about the “gliss and gloss” of the medal and that it’s all about the achievement for him.
“I think it’s alright [winning a gold medal], we weren’t really doing it so we could put medals around each other's necks,” he told RTÉ.
“It’s more the achievement of it than all the all glitz and gloss that goes with it, so I wouldn't be focusing on that type of thing.
“But, I’m happy that we had a good race and stayed in the boats unlike the Norwegians, the poor fellas fell out of the boat yesterday so we are happy that didn’t happen to us.”
Skibbereen now proudly claims to be a global Olympic powerhouse with athletes from the west Cork town boasting three Olympic medals in just 24 hours.
Put in context, Skibbereen's Tokyo games medal haul is equivalent to one medal for every 900 local residents, a startling level of global athletic achievement.
With a population of just over 2,700, Skibbereen has achieved the sporting equivalent of a featherweight winning the heavyweight title - with one hand tied behind their back.
Skibbereen's per capita medal ratio drops even lower if you take the 2016 Rio Olympics into account where local athletes won two silver medals.
Those three Tokyo medals - golds for Paul O'Donovan and Fintan McCarthy with a bronze medal going to Emily Hegarty - were also all won by members of the same Skibbereen Rowing Club.
Half of Ireland's entire medal haul so far from the Tokyo Games has been delivered by athletes from the same town and rowing club.
When asked if they found it hard to gel with one another, McCarthy said: “Not really, Paul is an absolute animal so it was handy enough to just sit behind him and try and emulate that.
While in Tokyo, O’Donovan said the duo enjoy playing scrabble, however he said they won’t get a chance to tonight.
“We won’t get a chance now, I wanted to because I’ve been losing the whole time and tonight was my chance, I was going to take all the winnings but we’ve media scheduled all afternoon so we’ll have to put it off until tomorrow, but I’ve got my dictionary in my pocket now so I’ll be well rehearsed.”
McCarthy’s parents Tom and Sue said there “are no words to describe” how proud they are of their son for winning an Olympic gold medal.
“It’s so overwhelming, we are absolutely delighted, they worked so hard,” Sue told RTÉ Radio 1’s Morning Ireland.
“There are no words to describe it, pride doesn’t cover it.”
Tom said he felt that the pair would win as they’ve “been on form all season.”
“And they didn’t let us down,” he added.
Fintan’s sister Caitlyn said it’s “crazy” that her brother has won an Olympic gold medal, as when he was young “he was never the sporty type”.
“It’s not something I would have imagined in a million years,” she said. “I think when he started rowing he put his mind to it, he wanted to be the best and thought there was no other point in doing it so he went out and did what he always said he was going to do.”
Fintan’s twin brother Jake, who is also a rower, said his brother’s win has “without a doubt” made him want to one day compete in the Olympics.
“I remember us watching the Rio Olympics and talking about it and ever since then a seed of belief was planted in his head,” he said.
“Watching that it was like something flicked inside of me, this desire to want to be there and you want to experience it.”
O’Donovan insisted that the Covid-19 restrictions had not impacted on their preparations.
“I don’t think it’s been tough, at all to be honest. We were planning on rowing this year anyway. So when they didn’t cancel the whole thing it suited us, it fitted in with our plan. We got to spend a lot of time at home in Skibbereen, which we don’t usually get because we are away going to regattas.”
28-year-old O’Donovan becomes the first-ever Irish athlete to win Olympic gold and silver medals and joins Pat O’Callaghan (gold in the hammer throw in 1928 and 1932) and Paddy Barnes (bronze in boxing in 2008 and 2012) as a medal winner at two different Olympics.
It is Ireland’s first Olympic gold medal since Kate Taylor's boxing win in 2012 and the first male Irish gold medallists since Michael Carruth in 1992.
O’Donovan’s partner Fintan McCarthy wins an Olympic gold on his debut.