It's been a couple of weeks since Prime Minister Justin Trudeau met U.S. President Donald Trump. And while most Canadians have moved on from parsing the minutiae of the Trump-Trudeau handshake, we're a long way from knowing just how that personal relationship will end up: will they be besties? Frenemies? Or straight-up rivals?

Below, some hints from past PM/POTUS relationships.

William Lyon Mackenzie King and Franklin Delano Roosevelt

(Overlap: 1935 -1945)

Rt. Hon. W.L. Mackenzie King and President Franklin D. Roosevelt speak on July 1936. (National Archives of Canada)

They're the two longest serving leaders of our respective nations, they both went to Harvard, and both stepped into power (back in, for Mackenzie King) just as the Great Depression started to ease.

Franklin Roosevelt (in office: 1933-1945) wanted closer ties with Canada, and William Lyon Mackenzie King (in office: 1921-1926, 1926-1930, 1935-1948) could see the shift of power tilting from Britain towards the U.S. The two opened up trading and signed mutual defence pacts, bringing Canada into the American sphere of influence, and helping bridge U.S./U.K. relations in the process.

When Roosevelt passed away in 1945, Mackenzie King even added his U.S. counterpart to his weekly seance sessions, along with his dogs, his mother and Sir Wilfrid Laurier.

Lyndon B. Johnson & Lester B. Pearson

(Overlap: 1963 -1968)

At Camp David, U.S. President Lyndon Johnson reportedly grabbed Prime Minister Lester Pearson by the collar, after Pearson suggested that the U.S. should cease bombing North Vietnam. (Associated Press)

They couldn't have been less alike, if you didn't count their overlapping terms as leaders and their shared first initials.

LBJ (in office: 1963–1969) was a giant, gregarious and blustery Texan, while LBP (in office: 1963–1968) was a short, intellectual diplomat who came within a Russian veto of being first Secretary General of the UN.

Sure they signed the AutoPact, but they were never going to be pals. Things even got physical in 1965 when Pearson made a speech at Temple University, proposing a "Pause for Peace." Later, at Camp David, an infuriated Johnson grabbed the Nobel Peace-Prize winning Prime Minister by the lapels and screamed: "Don't you come into my house and piss on my rug!"

Then again, Johnson often gave staff briefings while sitting on the toilet, so maybe Pearson got off lightly.

John F. Kennedy and John Diefenbaker

(Overlap: 1961–1963)

Stop me if this sounds familiar: a young, hip and popular new leader goes to meet a blustery old conservative one, and ... whatever the opposite of romance is? That's what happened.

John Diefenbaker (in office: 1957–1963) thought John F. Kennedy (in office: 1961–1963) was everything he despised: rich, privileged and arrogant. Kennedy found Diefenbaker boring, and snubbed The Chief for his rival, Lester B. Pearson.

So when Kennedy called the Prime Minister "Diefen-BAWKER", their relationship got downright frosty. And that was before Diefenbaker found a secret note briefing Kennedy on areas in which to "push" Canada, with the phrase "SOB" scribbled in the margin.

Ultimately Kennedy denied writing the phrase "SOB" because at the time he didn't know Diefenbaker was one.

Brian Mulroney and Ronald Reagan — overlap:1984–1989

Two Irish Conservatives walk into a ba ... llroom and emerge best friends.

If Diefenbaker/Kennedy are the nadir of Canada/U.S. leaders' relationships, then Brian Mulroney (in office: 1984-1993) and Ronald Reagan (in office: 1981-1989) are the pinnacle. A meeting that both sides saw as pivotal to national interest hinged on, it turns out, just being being Irish.

One slightly out of tune version of When Irish Eyes Are Smiling later, and our two countries had signed an historic agreement on the control of acid rain, and the Canada-US Declaration on Goods and Services, the first major step towards the 1988 Canada-U.S. Free Trade Agreement.

Canadian Prime Minister Brian Mulroney and U.S. President Ronald Reagan hold their first round of talks on Sunday, March 17, 1985 in Quebec City. (Scott Applewhite/Associated Press)

Bottom line, it's not necessary for our two leaders to get along, but we seem to get a lot more done when they do.

So if the Trudeau/Trump relationship starts to sour, it may not be the end of the world — and maybe they just need to sing a little tune.

Which Prime Minister/President Pairing had the most interesting relationship? Is there one you'd like to port into a steamy teen drama? Let us know in the comments below!