The call starts innocently enough: Californian representative Maxine Waters, warmly greets the voices on the line, whom a staffer identifies as Greta Thunberg and her father, Svante. They share a laugh about Ms Waters’s nickname, “Auntie Maxine”. The congresswoman praises her young caller for her climate change activism.

“You have made quite a big, big, big, big thunder on this issue. I am really, really very proud of you and the work that you’re doing,” Ms Waters is heard saying.

The congresswoman and her staff thought they had connected with Thunberg, the 17-year-old Swedish climate activist who was recently named Time magazine’s “Person of the Year”.

In reality, two 30-something Russians, Vladimir “Vovan” Kuznetsov and Alexei “Lexus” Stolyarov, were on the other end of the line. The duo describe themselves as comedians and pranksters, but they are widely suspected of having ties to the Russian government.

Audio from the call with Ms Waters was posted to the pair’s YouTube page on Thursday, along with a cartoon animating the approximately 10-minute interaction as part of their comedy video series called “Stars Save the Earth”.

Greta Thunberg inspires climate activists everywhere: In pictures Show all 12 1 /12 Greta Thunberg inspires climate activists everywhere: In pictures Greta Thunberg inspires climate activists everywhere: In pictures In the protest that started a movement, Greta skips school to sit outside of the Swedish parliament in Stockholm in order to raise awareness of climate change on 28 August 2018 Getty Greta Thunberg inspires climate activists everywhere: In pictures Greta speaks at the World Economic Forum in Davos on 25 January AFP/Getty Greta Thunberg inspires climate activists everywhere: In pictures Greta stages a protest at the World Economic Forum in Davos on 25 January Reuters Greta Thunberg inspires climate activists everywhere: In pictures Greta speaks at the House of Commons in London on 23 April PA Greta Thunberg inspires climate activists everywhere: In pictures Greta addresses to the occupation at Marble Arch in London on 21 April AFP/Getty Greta Thunberg inspires climate activists everywhere: In pictures Greta meets the pope on a visit to Rome Reuters Greta Thunberg inspires climate activists everywhere: In pictures Greta speaks at the senate in Rome on 18 April Reuters Greta Thunberg inspires climate activists everywhere: In pictures Greta addresses a debate of the EU Environment, Public Health and Food Safety committee at the European Parliament in Strasbourg on 16 April AFP/Getty Greta Thunberg inspires climate activists everywhere: In pictures Greta receives the Special Climate Protection Award at the German Film and Television awards in Berlin on 30 March AFP/Getty Greta Thunberg inspires climate activists everywhere: In pictures Greta attends a children's climate protest in Berlin on 29 March AFP/Getty Greta Thunberg inspires climate activists everywhere: In pictures Greta addresses a children's climate protest on 1 March in Hamburg Getty Greta Thunberg inspires climate activists everywhere: In pictures Greta attends a meeting for the Civil Society For rEUnaissance at the EU Charlemagne Building in Brussels on 21 February AFP/Getty

It’s unclear when exactly the call took place. Ms Waters’ office did not respond to questions seeking details about how the call was arranged or whether her office has screening or security protocols for phone calls. Ms Waters waved off the incident on Saturday, telling The Washington Post in an email statement:

“This was just another stupid prank by the same Russian operatives who have targeted many US elected officials, including representative Adam Schiff, senator Lindsey Graham, senator Mitch McConnell, and late-senator John McCain, and international heads of state such as Emmanuel Macron. The end.”

But security experts warn that what’s being passed off as prank-call mischief is really Russian misinformation meant to undermine the United States.

Mr Kuznetsov and Mr Stolyarov deny they’re Kremlin-backed agents with ties to Russian security forces, despite their pattern of frequently targeting people critical of Russia or the fact that, as two supposed pranksters, they’re able to reach powerful world leaders directly by phone.

“We work for ourselves, for nobody else,” Mr Stolyarov told the Guardian in 2016.

Whether the pair are agents of the Russian government, the kind of ruse they pulled on Ms Waters can accomplish two goals for Russia, according to Kathleen Hall Jamieson, a communications professor at the University of Pennsylvania and the author of the 2018 book, Cyberwar: How Russian Hackers and Trolls Helped Elect a President.

“The first [goal] is adding info. to a political dialogue in which discrediting one side is useful to Russia,” Ms Jamieson told The Post by phone. “The second is being able to make the argument to the rest of the world that US leaders are easily duped. Putin’s interests are served when US leaders are made to look foolish in the eyes of the world.”

Ms Waters was heard saying ‘I am really, really very proud of you and the work that you’re doing’ (Getty)

Mr Kuznetsov and Mr Stolyarov started pranking their own rich and famous countrymen around 2014, before moving on to targets like Elton John, Turkish President Recep Tayyip Erdogan and, more recently, Ms Graham and Mr Schiff. The men pose as prominent figures their targets would be keen to speak with, engage them in conversation and then post the audio to their YouTube channel.

The call to Ms Waters includes a mix of the absurd – the Thunberg impersonator mentions a climate strike in support of “Chon-go-Chango island” – and the overtly political.

Halfway through the call, the impersonators detail a fictional exchange between US president Donald Trump and Thunberg that they claim happened when both attended the UN climate summit in September. In it, they tell Ms Waters that the president made Thunberg cry when he said, “You’ll never achieve your goals like those congressional fools who accuse me”, and “I’ll tell you the truth: I really wanted to push the Ukraine president to put my competitor on trial. And he will go to trial with you, with [a bunch of] Democrats. . . . I would have a separate cage for all of you”.

“Oh my god, he mentioned the Ukrainian president?” Ms Waters is heard asking.

Mr Trump fell for a prank call in 2018 by a comedian pretending to be Robert Menendez (Getty)

The caller impersonating Thunberg’s father offers that they have an audio recording of Mr Trump’s remarks to Greta that they can provide to the congresswoman.

Ms Waters is heard assuring the callers that her colleagues are working diligently to gather facts in the impeachment case against Mr Trump. “[I]f the public knew he talked to Greta like that, and that she will never achieve – that will go against him, too,” she said.

Ms Waters ends the call by offering to arrange a meeting as quickly as possible, to which the callers agree.

Mr Schiff, Ms Waters’ congressional colleague and the ranking Democrat on the House Intelligence Committee, received a similar call from the two men in April 2017, when one posed as the speaker of Ukraine’s parliament, Andriy Parubiy, the Atlantic reported in 2018. On the call, the impersonator told Mr Schiff they had compromising material on Mr Trump, including nude photos of the president.

Mr Schiff is working with the FBI to investigate how the pranksters were able to hoax multiple people (AFP)

“We will try to work with the FBI to figure out, along with your staff, how we can obtain copies,” Mr Schiff reportedly responded. A spokesman for Mr Schiff later told the magazine that they suspected the call was “bogus” and had alerted security and law enforcement before agreeing to take it and after.

Despite those precautions, Republican opponents like representative Devin Nunes of California pointed to the existence of the call as evidence Democrats were being cavalier and incautious in gathering evidence against Mr Trump for the impeachment hearing.

“The point at which this enters the dialogue and can be used for a political attack has real consequences,” said Ms Jamieson.

Support free-thinking journalism and attend Independent events

Not all targets have been Democrats, but Ms Jamieson said it matters if the “pranksters” are reaching out to people involved in an ongoing investigation. She also advised watching to see whether reports of the stories are picked up and amplified by Russian government-controlled websites like RT and Sputnik.

“At that point, this is no longer a prank; this is engaging in disinformation,” she said.

A lingering question for Ms Jamieson – and perhaps many lawmakers’ offices – is whether voice recognition or other technology can advance to the point where it can help verify who is on the other end.

“There’s a real vulnerability when you’re talking to someone you can’t see. You wouldn’t want the president of the US, or someone who has the capacity to make significant leadership decisions, to be tricked by someone who isn’t who they allege they are,” Ms Jamieson said.

Mr Trump already fell victim to such a prank in 2018 when US comedian John Melendez, aka Stuttering John of “The Howard Stern Show”, claims to have reached the president on Air Force One by pretending to be senator Robert Menendez.