As they walked together into the ornate conference hall in Beijing, President Vladimir Putin looked around and declared in English to his American counterpart Barack Obama: "It's beautiful, isn't it?"
"Yes," came the US leader's monosyllabic reply, giving the Russian strongman the cold shoulder in response to his chummy pat on the back.
Earlier at the Asia-Pacific Economic Cooperation (Apec) summit last week, Mr Putin received a similar snub after he draped a shawl over China's First Lady Peng Li- yuan, only to watch her remove it soon after to hand it to an aide.
But none of this compared to arguably the frostiest moment of all in Beijing - the no-smiles, no- friend-of-mine handshake between China's President Xi Jinping and Japan's Prime Minister Shinzo Abe.
"Mr Xi looked like a man meeting his ex-wife's new boyfriend," was how Professor John Delury of South Korea's Yonsei University described it to the Wall Street Journal.
Both men seemed at pains to play it cool, lest they offend nationalist sentiment at home, which they have foolishly allowed to be whipped up for political effect in recent times.
All of this made for lively Twitter chatter amid the flurry of back- to-back summit meetings through the past week, as leaders shuttled from Beijing to Brisbane, with hundreds of aides, security officers and journalists in tow.
But it is worth pondering if these awkward moments among world leaders reflect just so much media sound and fury, or whether they signify deeper rifts which point to trouble ahead.
An indication came barely a day after the Beijing summit. At a meeting of the United Nations Security Council on Wednesday, Ms Samantha Power, US envoy to the UN, declared: "The pattern is clear. Where Russia has made commitments, it has failed to meet them. Russia has negotiated a peace plan and then systematically undermined it at every step. It talks of peace, but it keeps fuelling war."
She was speaking after Nato accused Russia of sending troops, artillery and air defence systems across the border into Ukraine.
With the situation in Ukraine coming to a head, whether the US and Russia will be able to avert a catastrophe will depend in no small measure on whether Mr Obama and Mr Putin are able to keep up a working relationship.
In a crunch, personal relations and chemistry between the two leaders will count, just as when former British Prime Minister Margaret Thatcher used to declare that then Soviet supremo Mikhail Gorbachev was a man she "could do business with".
Similarly, the evident mutual respect and warmth between the two present prime ministers of Singapore and Malaysia have often been cited as having helped the neighbours push through ambitious joint projects, such as plans for a high-speed rail link between Singapore and Kuala Lumpur.
Indeed, many have also been hoping that Mr Xi and Mr Obama would be able to live up to their rosy pledge to forge a "new type of superpower relations" at their "shirtsleeves summit" in Sunnylands, California, in June last year.
So the unexpected announcement in Beijing of a secretly negotiated deal to curb carbon dioxide emissions, with China agreeing to cap its emissions around 2030 while the US would make deep cuts by 2025, came as a pleasant surprise.
There were few details on just how this will be done, as well as doubts about whether the effort goes far enough, but the pact was nonetheless hailed as a major step forward, if only because it signalled the two leaders' willingness to work together to tackle a shared global challenge.
The idea for collaboration on common goals as a way to foster the new form of great power relations has been pushed by former US Treasury Secretary Hank Paulson for some time.
He summed up the case for this in a Wall Street Journal report this way: "Half of all the buildings in the world are going up in China; buildings account for 40 per cent of global greenhouse gas emissions, of which China is the biggest producer. Construct those buildings to a higher standard and you're helping to fix a megaproblem."
Perhaps Mr Obama and Mr Xi should rope in Japan, known for its Cool Biz initiatives to curb energy wastage, and urge Mr Abe to marshall his country's technological prowess for this common cause.
Certainly, there is much need for closer collaboration and warmer ties between China and Japan, as evidenced by the stiff, stand-offish encounter between Mr Xi and Mr Abe. This was painful to watch, not just for what it said about the lack of rapport between them, but also for how it made plain the sad state of relations between these Asian neighbours.
Many observers were thankful that the meeting even took place at all. It required arduous negotiations to reach a vague four-points agreement, in which Japan acknowledged that there were "different positions" over the islands both sides claim as their own. The joint statement also said the two countries would work at overcoming "political difficulties" in the spirit of "squarely facing history".
But just days after that awkward summit meeting, Mr Abe was calling for stepped-up trilateral defence ties with the US and Australia to beef up security in the Asia-Pacific, which will no doubt draw the ire of Beijing.
So is the Asia-Pacific Dream just a pipe dream? Or might it end up a nightmare, if we are all not careful?
Taking a leaf from Mr Paulson's book, perhaps getting down to work on some commonly shared goals, such as tackling climate change, might just be the way to keep things moving forward.
Ultimately, though, some facing up to history is going to be needed. To make this happen, Mr Xi and Mr Abe would be wise to take up the call by Singapore's Ambassador-at-Large Tommy Koh "to show statesmanship" by referring their disputes to the UN for independent arbitration.
Doing so would be the best way to lift the historical burdens from the shoulders of a younger generation of Asians, eager to see their region move forward, rather than being forever shackled by the costly mistakes, in both lives and treasure, of their forefathers. Certainly, younger Asians should not be consigned to repeating those mistakes, simply because segments of society are unable or unwilling to look beyond the painful past to embrace a more positive future.
To my mind, apart from a new type of superpower ties, Asia needs a new model of regional relations, if it is to manage the unique challenge of a rising China and a resurgent Japan happening at the same time.
Mr Xi has spoken expansively of an "Asia-Pacific Dream". But for such a dream to be realised, it has to fit the nature of our 21st Century times, where young people around the world want to connect, collaborate and change the future for the better. Age-old ideas of great power rivalry, tributes and homage, and ultimately who sits at the centre of it all in the regional scheme of things, would have to be set aside.
No doubt, many will be sceptical that this grandiose summit talk will amount to much, not least since Messrs Xi, Abe, and Putin have other issues to address at home. So too do the newly elected leaders of India and Indonesia. Even Mr Obama seems to be bracing himself for some domestic fights, on issues such as immigration reform, despite the drubbing his party suffered at the mid-term polls earlier this month.
Yes, all politics is local, as they say. But given the big geopolitical and security challenges we face today, the best legacy that the world's top leaders, now gathered in Brisbane for the G-20 summit, can leave might well be to figure out how to get along, and set their countries' relations on a stable course for the future.
Follow Warren Fernandez on Twitter @theSTeditor