The prank phone call, which is thought to have lasted 11 minutes, was made by notorious Russian pranksters Vladimir Kuznetsov and Alexey Stolyarov. The men told The Associated Press (AP) they had pranked the Democrat Party leader hopeful, and posted the audio to Youtube.
Mr Kuznetsov and Mr Stolyarov have a history of targeting US politicians.
They have in the past been accused of having ties to the Kremlin, a notion they have repeatedly denied.
The conversation with the Vermont socialist began warmly, with Mr Stolyarov taking the role of Svante Thunberg, Ms Thunberg’s father.
An unknown woman played the role of Great.
The three spoke about the possibility of Ms Thunberg endorsing Mr Sanders’ presidential campaign.
Mr Sanders said: “Let us continue to talk and when you come to the United States.
“I will bring some people together and we can do some interesting things, and if you wanted to make a statement in support of my candidacy and the program we have outlined for climate change, I would be very very appreciative.”
Things took a satirical turn after the Ms Thunberg imposter quizzed the senator about his visit to Soviet Russia in 1988.
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At some point during the rant Mr Sanders hung up the phone.
The call itself took place in early December, but the duo decided to wait two months until releasing the audio because of mr Sanders’ success in Iowa and New Hampshire, according to AP.
A representative for the campaign didn’t comment on the authenticity of the call.
Federal law enforcement officials were alerted in November that several Democrats had received calls from someone believed to be outside the US.
Many of these calls came from someone claiming to represent Ms Thunberg, and consisted of someone trying to set up calls or in-person meetings with members of Congress, a US official told AP.
While some of the incidents were reported to the FBI, others were disclosed to the Capitol Police.
Mr Kuznetsov said the call was one of many in the comedy duo’s new project dubbed “Stars Save the Earth”.
In this new venture, the pair call high-ranking politicians and celebrities pretending to be the teenage climate activist.
Mr Kuznetsov said: “Many laugh at Bernie Sanders and say that he is a KGB agent and wants to build communism in the U.S. Since he calls himself a democratic socialist, we decided to play up this topic — the topic of Sanders being a recruited Russian agent.”
Meanwhile, Mr Stolyarov insisted the pranksters did not want to influence the presidential race in the US.
Mr Kuznetsov said they didn’t expect any repercussions for the prank, and said: “It’s not illegal, and we’re well known in the US.”