Harper thought he was chatting with Quebec politician Francois Legault in a French-language conversation to be aired Monday.
The prime minister congratulated the third-party leader for fighting the new Parti Quebecois government's plan to increase taxes on high income-earners while, at the same time, he cautioned against toppling the minority government too fast.
Quebec's so-called Masked Avengers say they got the prime minister on the phone Thursday while he was in New York City to receive an award for international statesmanship.
They say they did it by posing as the Coalition party leader, Legault, and pretending not only to be seeking Harper's advice but also to be offering congratulations on the award.
The comedy duo said it's grateful to the United Nations for its very successful week.
First, officials at the global body put them through to secretary-general Ban-Ki Moon in a stunt Wednesday that aired the following day. Next, they gave the duo phone numbers that they used to track down the prime minister.
"It was really thanks to the United Nations. It's fun to have an organization like that, which really lends a hand to Quebec comedians," said Marc-Antoine Audette, one member of the pair, in an interview Friday.
"(They) gave us a lot of direct numbers to Ottawa, and to the Conservative party and to the government in general."
The jokesters weren't satisfied with merely pranking two famous leaders. They also tried pulling a fast one on the entire UN, by fibbing to officials that the contact information for the Government of Canada had changed. They gave them their own numbers as a replacement.
"So for about an hour or two hours on Wednesday, if there had been any problems at the UN — they would have called us, not Stephen Harper," Audette said.
Fortunately, there was no diplomatic incident.
But they did get Harper on the phone Thursday.
They chatted with Harper staffers about the recent Quebec election and said they wanted the prime minister's advice on dealing with the province's new minority government. Harper's staffers were, according to Audette, relatively blunt while discussing the Parti Quebecois.
But he said the prime minister, who is generally cautious in his public statements and was especially careful not to comment at all on Quebec politics during the recent election, was more diplomatic.
An official in Ottawa confirmed the gist of the conversation. Pretending to be Legault, the prankster apparently suggested that he planned to take down the PQ minority government as quickly as possible.
Harper urged him to be patient.
"Mr. Harper, when he spoke to 'Francois Legault,' he said it in a formal way that it was not a good idea to topple the PQ right away," Audette said.
He would not reveal too much about the conversation because he said he wanted to save some surprises for listeners on Monday. Eventually, after about "five or 10 minutes," the prime minister was made aware something was up.
Harper apparently took it in stride.
"He was a good sport," Audette said.
"We know that the prime minister is a very serious man. He was very nice, but serious... He said, 'Ah, so it's a joke.' He greeted our audience and that was it."
The federal official confirmed that Harper advised against immediately toppling the PQ. He also offered one more tidbit from the chat: he said Harper "congratulated" the fake Legault on his Coalition party's stance against the PQ's planned tax hikes for people earning over $130,000.
In a tweet Friday afternoon, a Harper spokesman asked the so-called Masked Avengers when they were going to air the interview between the prime minister and the "fake Francois Legault." He appeared not to take the stunt too seriously.
"Well played," Harper spokesman Andrew MacDougall wrote a day earlier on Twitter.
"The PM always welcomes a chance to speak with the people of Quebec but we do usually like to know about it first."
It was the second Harper-related stunt of the week for the Quebec pair.
On Thursday, Audette and Sebastien Trudel announced that they had posed as the prime minister and managed to get the secretary general of the United Nations on the phone.
They proudly recounted how Ban-Ki Moon was rushed out of an important meeting to speak to them and that he became confused when the fake "Harper" complained that he was too busy combing his hair with crazy glue.
That's how they got contact information for the prime minister's entourage.
The Avengers' past victims include former Bloc Quebecois leader Gilles Duceppe, former American vice-presidential candidate Sarah Palin and business tycoon Donald Trump.
-With file from Alexander Panetta
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