I literally ran into Mulroney at Trudeau airport. I was going up the stairs in the Maple Leaf Lounge and he was crossing the top of the staircase (having taken the elevator). I wasn't looking at where I was going and walked into him. He laughed. His handler (an airport person) was less impressed. This was a couple years ago (so long after he was PM).
We had a chalet next door to Martin (long before he was anything) in the Laurentians. One weekend, the hill up was totally iced over and the cars couldn't make it up. So, he piggybacked me up the hill. I have no memory of this - my parents told me the story when he was running for PM.
I played tether-ball with Trudeau senior and had a kiss with Trudeau junior (we were both under 10 - it was a dare) at summer camp.
When Chretien was Leader of the Opposition, he attended my school's Model UN and I was responsible for showing him around.
For US Presidents...
I was touring the WH when Reagan landed in Marine One.
Clinton gave a speech at the retirement community where my grandparents spent the winter, while I was there visiting. So, we went to see it. Both he and Hilary were there.